研究者データベース

研究者情報

マスター

アカウント(マスター)

  • 氏名

    三浦 章(ミウラ アキラ), ミウラ アキラ

所属(マスター)

  • 工学研究院 応用化学部門 無機材料化学分野

所属(マスター)

  • 工学研究院 応用化学部門 無機材料化学分野

独自項目

syllabus

  • 2020, 大学院共通授業科目(一般科目):自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, X線結晶構造解析,電子顕微鏡,中性子回折,X線吸収分光,固体NMR
  • 2020, 物質構造解析学特論, Structural Analysis of Inorganic Materials, 修士課程, 工学院, X線結晶構造解析,電子顕微鏡,中性子回折,X線吸収分光,固体NMR
  • 2020, 物質構造解析学特論, Structural Analysis of Inorganic Materials, 修士課程, 総合化学院, X線結晶構造解析,電子顕微鏡,中性子回折,X線吸収分光,固体NMR
  • 2020, 応用化学特別講義, Advanced-Applied Chemistry, 修士課程, 総合化学院, energy conversion devices, energy storage devices, solar cells, all nano-structures, solid state batteries
  • 2020, 応用化学特別講義, Advanced-Applied Chemistry, 修士課程, 総合化学院, Materials, computational, data analysis
  • 2020, 物質構造解析学特論, Structural Analysis of Inorganic Materials, 博士後期課程, 工学院, X線結晶構造解析,電子顕微鏡,中性子回折,X線吸収分光,固体NMR
  • 2020, 先端総合化学特論Ⅱ, Modern Trends in Chemical Sciences and Engineering II, 博士後期課程, 総合化学院, energy conversion devices, energy storage devices, solar cells, all nano-structures, solid state batteries
  • 2020, 先端総合化学特論Ⅱ, Modern Trends in Chemical Sciences and Engineering II, 博士後期課程, 総合化学院, Materials, computational, data analysis
  • 2020, 国際交流Ⅰ, Arts and Science Courses in English 1, 学士課程, 国際本部, advanced inorganic materials, ceramics, glasses, applications
  • 2020, 工学特別講義, Special Lecture on Engineering, 学士課程, 工学部, energy conversion devices, energy storage devices, solar cells, all nano-structures, solid state batteries
  • 2020, 化学英語, English for Chemistry, 学士課程, 工学部, 化学,英語,単語,表記法
  • 2020, 応用化学学生実験Ⅱ, Applied Chemistry Laboratory Ⅱ, 学士課程, 工学部, 固相反応、焼結、固溶体、X線回折、電子顕微鏡、熱分析、セラミックス
  • 2020, 工学特別講義, Special Lecture on Engineering, 学士課程, 工学部

researchmap

プロフィール情報

学位

  • 博士(工学)(2007年12月 北海道大学)

プロフィール情報

  • プロフィール

    窒化物や複合アニオン化合物などの非酸化物を中心に、新規合成法の創出を基盤にした触媒、全固体リチウム電池、超伝導体等の新規材料開発を行っています。また、近年発展した計算機データーベースを利用した材料設計に向け、結晶構造から合成反応を理解し反応を設計する手法の探索を進めています。

    Google Scholar: https://scholar.google.com/citations?hl=en&user=_vPBvrAAAAAJ&view_op=list_works

  • 三浦, ミウラ
  • 章, アキラ
  • ID各種

    201401080174757447

対象リソース

業績リスト

研究キーワード

  • 合成反応設計   複合アニオン化合物   窒化物   材料化学   結晶構造解析   無機合成化学   

研究分野

  • ナノテク・材料 / 無機物質、無機材料化学
  • ナノテク・材料 / 無機材料、物性

経歴

  • 2021年10月 - 現在 JSTさきがけ研究員(兼任)
  • 2020年03月 - 2025年03月 北海道大学 大学院工学研究院 准教授
  • 2016年04月 - 2020年03月 北海道大学 大学院工学研究院 助教
  • 2019年09月 - 2019年10月 ローレンスバークレー国立研究所 客員研究員
  • 2014年09月 - 2016年03月 北海道大学 大学院工学研究院 特任助教
  • 2010年12月 - 2014年08月 山梨大学 大学院医学工学総合研究部 附属クリスタル科学研究センター 助教
  • 2010年02月 - 2010年11月 アーヘン工科大学 博士研究員(Humboldt Research Fellowship)
  • 2008年01月 - 2009年12月 コーネル大学 博士研究員

学歴

  • 2006年04月 - 2007年12月   北海道大学   大学院工学研究院   物質工学専攻博士後期課程早期修了
  • 2004年04月 - 2006年03月   北海道大学   大学院工学研究院   物質化学専攻修士課程修了
  • 2000年04月 - 2004年03月   北海道大学   工学部   応用化学科

委員歴

  • 2020年08月 - 現在   物質科学フロンティアを開拓するAmbitiousリーダー育成プログラム 7期生メンター
  • 2020年04月 - 現在   物質科学フロンティアを開拓するAmbitiousリーダー育成プログラム   QE委員
  • 2020年04月 - 現在   物質科学フロンティアを開拓するAmbitiousリーダー育成プログラム   4期生メンター
  • 2019年03月 - 現在   日本セラミックス協会   行事企画委員
  • 2014年12月 - 現在   北海道大学物質科学フロンティアを開拓するAmbitiousリーダー育成プログラム 教務専門員会   教務委員
  • 2014年12月 - 現在   北海道大学物質科学フロンティアを開拓するAmbitiousリーダー育成プログラム 広報専門委員会   広報委員
  • 2015年09月 - 2021年03月   物質科学フロンティアを開拓するAmbitiousリーダー育成プログラム   2期生メンター
  • 2018年04月 - 2019年03月   物質科学フロンティアを開拓するAmbitiousリーダー育成プログラム   独立ラボメンター
  • 2017年04月 - 2018年03月   電気化学会北海道支部   幹事
  • 2016年04月 - 2018年03月   日本セラミックス協会ガラス部会   事務局長補佐
  • 2018年01月   化学系学協会北海道支部2018年冬季研究発表会   実行委員
  • 2018年01月   化学系学協会北海道支部2020年冬季研究発表会   実行委員
  • 2017年04月 - 2017年08月   第49回日本セラミックス協会ガラス部会夏季若手セミナー 世話人
  • 2015年04月 - 2017年03月   応用化学学科広報員会   広報委員
  • 2015年10月 - 2016年01月   HU-UCB Joint Symposium 世話人
  • 2015年10月 - 2016年01月   HU-UCB joint symposium on chemical sciences and engineering   実行委員
  • 2015年04月 - 2015年11月   第41回固体イオニクス討論会   世話人
  • 2015年04月 - 2015年10月   日本セラミックス協会東北北海道支部 第23回北海道地区ミナー2015   世話人
  • 2015年04月 - 2015年10月   日本セラミックス協会第28回秋季シンポジウム 複合イオン化合物の創製と機能   オーガナイザー
  • 2012年04月 - 2014年03月   山梨大学工学部 コンピュータ処理専門委員会   委員
  • 2012年01月 - 2012年01月   第50回セラミックス基礎科学討論会   現地実行委員
  • 2011年12月 - 2011年12月   第6回日本フラックス成長研究発表会   実行委員会

受賞

  • 2021年03月 北海道大学大学院工学研究院 若手教員奨励賞授賞
     
    受賞者: 三浦 章
  • 2020年12月 日本化学会北海道支部 日本化学会北海道支部奨励賞
     硫化物および酸硫化物の合成手法開拓と機能性の発現 
    受賞者: 三浦章
  • 2018年06月 日本セラミックス協会 21世紀記念 倉田 元治賞
     
    受賞者: 三浦 章
  • 2017年06月 日本セラミックス協会 日本セラミックス協会賞進歩賞
     窒化物・酸窒化物における合成プロセスの開発および理論の構築 
    受賞者: 三浦 章
  • 2015年04月 日本物理学会 Most Cited Articles in 2014 from Vol. 82 (2013)
  • 2014年03月 日本セラミックス協会 2014年年会最優秀ポスター発表賞
     
    受賞者: 三浦 章
  • 2012年09月 セラミックス協会第25回秋季シンポジウム 特定セッション優秀発表賞
     
    受賞者: 三浦 章
  • 2012年01月 50th Anniversary Symposium on Basic Science of Ceramics Presentation Award
     
    受賞者: 三浦章
  • 2011年12月 第6回日本フラックス成長研究発表会 発表賞
     
    受賞者: 三浦 章
  • 2005年10月 セラミックス協会東北北海道支部研究発表会 学生優秀発表賞
     
    受賞者: 三浦 章

論文

  • Koki Kinami, Yuji Hanada, Masanori Nagao, Akira Miura, Shigeto Hirai, Yuki Maruyama, Satoshi Watauchi, Isao Tanaka
    Journal of Alloys and Compounds 883 160812 - 160812 2021年11月 [査読有り]
  • Nataly Carolina Rosero-Navarro, Haruna Watanabe, Akira Miura, Kiyoharu Tadanaga
    Journal of the European Ceramic Society 41 13 6767 - 6771 2021年10月 [査読有り]
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Sol-Gel Science and Technology 2021年09月16日 [査読有り]
  • Shinji Noguchi, Jin Odahara, Hayato Sakai, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Inorganic Chemistry 60 17 12753 - 12758 2021年09月06日 [査読有り]
  • Lauren Blanc, Christopher J. Bartel, Haegyeom Kim, Yaosen Tian, Hyunchul Kim, Akira Miura, Gerbrand Ceder, Linda F. Nazar
    ACS Materials Letters 3 8 1213 - 1220 2021年08月02日 [査読有り]
  • Hiroaki Ito, Kazuki Shitara, Yongming Wang, Kotaro Fujii, Masatomo Yashima, Yosuke Goto, Chikako Moriyoshi, Nataly Carolina Rosero‐Navarro, Akira Miura, Kiyoharu Tadanaga
    Advanced Science 8 15 2101413 - 2101413 2021年08月 [査読有り]
  • Keisuke Shinozaki, Yosuke Goto, Kazuhisa Hoshi, Ryosuke Kiyama, Naoto Nakamura, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Hidetomo Usui, Yoshikazu Mizuguchi
    ACS Applied Energy Materials 4 5 5155 - 5164 2021年05月24日 [査読有り]
  • Akira Miura, Christopher J. Bartel, Yosuke Goto, Yoshikazu Mizuguchi, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yongming Wang, Toshie Yaguchi, Manabu Shirai, Masanori Nagao, Nataly Carolina Rosero‐Navarro, Kiyoharu Tadanaga, Gerbrand Ceder, Wenhao Sun
    Advanced Materials 2100312 - 2100312 2021年05月05日 [査読有り]
  • Hiroki ITO, Akira MIURA, Yosuke GOTO, Yoshikazu MIZUGUCHI, Chikako MORIYOSHI, Yoshihiro KUROIWA, Nataly Carolina ROSERO-NAVARRO, Kiyoharu TADANAGA
    Journal of the Ceramic Society of Japan 129 5 249 - 253 2021年05月01日 [査読有り]
  • Marcela Calpa, Hiroshi Nakajima, Shigeo Mori, Yosuke Goto, Yoshikazu Mizuguchi, Chikako Moriyoshi, Yoshihiro Kuroiwa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Inorganic Chemistry 2021年04月29日 [査読有り]
  • Ichiro Yamane, Kota Sato, Ryoichi Otomo, Takashi Yanase, Akira Miura, Taro Nagahama, Yuichi Kamiya, Toshihiro Shimada
    Nanomaterials 11 4 1040 - 1040 2021年04月19日 [査読有り]
     
    A metal–organic framework (MOF) consisting of Cu-benzenetricarboxylic acid was processed under ultrahigh pressure (5 GPa) and at temperature of up to 500 °C. The products were characterized with TEM, FTIR, and XAFS. The decomposition of the MOF started at 200 °C at 5 GPa. This temperature was much lower than that in the vacuum. Single-nanometer Cu nanoparticles were obtained in carbon matrix, which was significantly smaller than the Cu particles prepared at ambient pressure. The catalytic activity for Huisgen cycloaddition was examined, and the sample processed at 5 GPa showed a much improved performance compared with that of the MOF-derived Cu nanoparticles prepared without high pressure.
  • Yuta Fujii, Hiroaki Ito, Akira Miura, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga, Li Lu
    Functional Materials Letters 14 03 2141005 - 2141005 2021年04月 [査読有り]
     
    We report the fast discharge–charge cycle of micro-sized FePS3 electrode particles in all-solid-state batteries (ASSBs) using sulfide electrolytes at 80C. At a current density of 2.04 mA cm[Formula: see text], corresponding to approximately 1 C, the capacity of the FePS3 electrodes reached [Formula: see text]180 mAh g[Formula: see text] without any electron or lithium-ion conductive additives. Galvanostatic intermittent titration technique (GITT) measurements showed a stable diffusion path of FePS3 represented by the product of the diffusion coefficient and square of the surface area. These electrochemical properties were compared with those of FeS, whose capacity was lower because of its unstable diffusion path.
  • Yuji Masubuchi, Suzuka Miyazaki, Kotaro Fujii, Masatomo Yashima, Akira Miura, Mikio Higuchi
    Journal of Solid State Chemistry 296 122000 - 122000 2021年04月 [査読有り]
  • F. A. Vásquez, N. C. Rosero-Navarro, A. Miura, R. Jalem, Y. Goto, M. Nagao, Y. Tateyama, K. Tadanaga, J. A. Calderón
    ACS Applied Materials & Interfaces Accepted 2021年03月16日 [査読有り]
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Randy Jalem, Yoshitaka Tateyama, Kiyoharu Tadanaga
    Applied Materials Today 22 100918 - 100918 2021年03月 [査読有り]
  • Yosuke Goto, Shota Nakanishi, Yusuke Nakai, Takeshi Mito, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Hidetomo Usui, Tatsuma D. Matsuda, Yuji Aoki, Yoshifumi Nakacho, Yuto Yamada, Kiyoshi Kanamura, Yoshikazu Mizuguchi
    Journal of Materials Chemistry A Accepted 2021年 [査読有り]
     

    The physical and chemical properties of Li1−xSn2+xP2 are affected by Li/Sn mixed occupation with local ordering.

  • Riku Maniwa, Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Materials Chemistry A 9 1 400 - 405 2021年 [査読有り]
     

    We report the liquid-phase synthesis of sulfide solid electrolytes from Li2S and P2S5 using anisole at 200–300 °C under microwave irradiation, in which β-Li3PS4 and Li7P3S11 were directly precipitated in anisole in 30 min.

  • Kazuhisa Hoshi, Shunsuke Sakuragi, Takeshi Yajima, Yosuke Goto, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yoshikazu Mizuguchi
    Condensed Matter 5 4 81 - 81 2020年12月11日 [査読有り]
  • Aichi Yamashita, Rajveer Jha, Yosuke Goto, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Chizuru Kawashima, Kouhei Ishida, Hiroki Takahashi, Yoshikazu Mizuguchi
    Scientific Reports 10 1 2020年12月01日 [査読有り][通常論文]
     
    © 2020, The Author(s). Polycrystalline samples of Sr0.5RE0.5FBiS2 (RE: La, Ce, Pr, Nd, and Sm) were synthesized via the solid-state reaction and characterized using synchrotron X-ray diffraction. Although all the Sr0.5RE0.5FBiS2 samples exhibited superconductivity at transition temperatures (Tc) within the range of 2.1–2.7 K under ambient pressure, the estimated superconducting volume fraction was small, which indicates non-bulk nature of superconductivity in those samples under ambient pressure. A dramatic increase in shielding fraction, which indicates the emergence of the bulk superconductivity was achieved by applying external hydrostatic pressures. We found that two phases, low-P phases with Tc = 2.5–2.8 K and high-P phases with Tc = 10.0–10.8 K, were induced by the pressure effect for samples with RE = La, Ce, Pr, and Nd. Pressure-Tc phase diagrams indicated that the critical pressure for the emergence of the high-P phase tends to increase with decreasing ionic radius of the doped RE ions, which was explained by the correlation between external and chemical pressure effects. According to the high-pressure X-ray diffraction measurements of Sr0.5La0.5FBiS2, a structural phase transition from tetragonal to monoclinic also occurred at approximately 1.1 GPa. Bulk superconducting phases in Sr0.5RE0.5FBiS2 induced by the external hydrostatic pressure effect are expected to be useful for understanding the effects of both external and chemical pressures to the emergence of bulk superconductivity and pairing mechanisms in BiCh2-based superconductors.
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kota Terai, Futoshi Utsuno, Kiyoharu Tadanaga
    Chemistry of Materials 32 22 9627 - 9632 2020年11月24日 [査読有り]
  • Nataly Carolina Rosero-Navarro, Ryunosuke Kajiura, Akira Miura, Kiyoharu Tadanaga
    ACS Applied Energy Materials 3 11 11260 - 11268 2020年11月23日 [査読有り]
  • Masanori Nagao, Akira Miura, Yoichi Horibe, Yuki Maruyama, Satoshi Watauchi, Yoshihiko Takano, Isao Tanaka
    Solid State Communications 321 114051 - 114051 2020年11月 [査読有り]
  • Kazuhisa Hoshi, Motoi Kimata, Yosuke Goto, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Masanori Nagao, Yoshikazu Mizuguchi
    Journal of Physics Communications 4 9 095028 - 095028 2020年10月06日 [査読有り]
  • Rajveer Jha, Yosuke Goto, Ryuji Higashinaka, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yoshikazu Mizuguchi
    Physica C: Superconductivity and its Applications 576 1353731 - 1353731 2020年09月 [査読有り][通常論文]
  • Yuma Fujita, Koki Kinami, Yuji Hanada, Masanori Nagao, Akira Miura, Shigeto Hirai, Yuki Maruyama, Satoshi Watauchi, Yoshihiko Takano, Isao Tanaka
    ACS Omega 5 27 16819 - 16825 2020年07月14日 [査読有り][通常論文]
  • Akira MIURA, Sho ISHIYAMA, Daiju KUBO, Nataly Carolina ROSERO-NAVARRO, Kiyoharu TADANAGA
    Journal of the Ceramic Society of Japan 128 7 336 - 339 2020年07月01日 [査読有り][通常論文]
  • Ryosuke Kiyama, Yosuke Goto, Kazuhisa Hoshi, Rajveer Jha, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Tatsuma D. Matsuda, Yuji Aoki, Yoshikazu Mizuguchi
    Journal of the Physical Society of Japan 89 6 064702 - 064702 2020年06月15日 [査読有り][通常論文]
  • Nataly Carolina Rosero-Navarro, Ryunosuke Kajiura, Randy Jalem, Yoshitaka Tateyama, Akira Miura, Kiyoharu Tadanaga
    ACS Applied Energy Materials 2020年05月27日 [査読有り][通常論文]
  • Kota Morino, Yosuke Goto, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yoshikazu Mizuguchi
    Materials 13 9 2164 - 2164 2020年05月07日 [査読有り]
     
    We report the synthesis and thermoelectric transport properties of As-doped layered pnictogen oxyselenides NdO0.8F0.2Sb1−xAsxSe2 (x ≤ 0.6), which are predicted to show high-performance thermoelectric properties based on first-principles calculation. The crystal structure of these compounds belongs to the tetragonal P4/nmm space group (No. 129) at room temperature. The lattice parameter c decreases with increasing x, while a remains almost unchanged among the samples. Despite isovalent substitution of As for Sb, electrical resistivity significantly rises with increasing x. Very low thermal conductivity of less than 0.8 Wm−1K−1 is observed at temperatures between 300 and 673 K for all the examined samples. For As-doped samples, the thermal conductivity further decreases above 600 K. Temperature-dependent synchrotron X-ray diffraction indicates that an anomaly also occurs in the c-axis length at around 600 K, which may relate to the thermal transport properties.
  • Akira Miura, Hiroaki Ito, Christopher J. Bartel, Wenhao Sun, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga, Hiroko Nakata, Kazuhiko Maeda, Gerbrand Ceder
    Materials Horizons 7 5 1310 - 1316 2020年05月01日 [査読有り][通常論文]
     

    By altering the thermodynamic landscape, metathesis enables the rapid and selective synthesis of MgCr2S4 thiospinel, a compelling Mg-cathode material that is laborious to make via traditional ceramic synthesis routes.

  • Fujii, Yuta, Akira, Miura, Misaki, Kobayashi, Rosero-Navarro, Nataly Carolina, Li, Minchan, Sun, Jianguo, Kotobuki, Masatoshi, Lu, Li, Tadanaga, Kiyoharu
    Journal of Power Sources 449 15 227576 - 227576 2020年02月 [査読有り][通常論文]
  • W. I, U. WITHANAGE, Nobuhiro Kumada, Takahiro Takei, Sayaka YANAGIDA, Kiyoharu Tadanaga, Akira Miura, Nataly Carolina Rosero-Navarro, Masaki Azuma
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 128 1 46 - 50 2020年01月01日 [査読有り][通常論文]
  • Nagao, Masanori, Miura, Akira, Urushihara, Daisuke, Maruyama, Yuki, Goto, Yosuke, Mizuguchi, Yoshikazu, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Wang, Yongming, Watauchi, Satoshi, Asaka, Toru, Takano, Yoshihiro, Tadanaga, Kiyoharu, Tanaka, Isao
    Frontiers in Chemistry 8 00044  2020年 [査読有り][通常論文]
  • Hajime Ito, Koji Kubota, Yadong Pang, Akira Miura, Hajime Ito
    Science 366 6472 1500 - 1504 2019年12月20日 [査読有り][通常論文]
  • Koki Kinami, Yuji Hanada, Masanori Nagao, Akira Miura, Yosuke Goto, Yuki Maruyama, Satoshi Watauchi, Yoshihiko Takano, Isao Tanaka
    Crystal Growth & Design 19 11 6136 - 6140 米国化学会 2019年11月06日 [査読有り][通常論文]
  • Kubo Daiju, Igarashi Kohei, Ishiyama Sho, Rosero Navarro, Nataly Carolina, Miura Akira, Higuchi Mikio, Tadanaga Kiyoharu
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 127 11 788 - 792 2019年11月 [査読有り][通常論文]
  • Ishiyama, Sho, Rosero-Navarro, Nataly Carolina, Miura, Akira, Tadanaga, Kiyoharu
    Materials Research Bulletin Volume 119, November 2019, 110561 119 110561  2019年11月 [査読有り][通常論文]
  • Pressure-induced superconductivity in the layered pnictogen diselenide NdO0.8F0.2Sb1-xBixSe2 (x=0.3 and 0.7)
    Matsumoto Ryo, Goto Yosuke, Yamamoto Sayaka, Sudo Kenta, Usui Hidetomo, Miura Akira, Moriyoshi Chikako, Kuroiwa Yoshihiro, Adachi Shintaro, Irifune Tetsuo, Takeya Hiroyuki, Tanaka Hiromi, Kuroki Kazuhiko, Mizuguchi Yoshikazu, Takano Yoshihiko
    PHYSICAL REVIEW B 100 9 094528  2019年09月 [査読有り][通常論文]
  • Fujii, Yuta, Ramirez, Daniel, Rosero-Navarro, Nataly Carolina, Miura, Akira, Jaramillo, Franklin, Tadanaga, Kiyoharu
    ACS Applied Energy Materials 2 9 6569 - 6576 2019年08月 [査読有り][通常論文]
  • Kumada, Nobuhiro, Imase, Akihito, Yanagida, Sayaka, Takei, Takahiro, Miura, Akira, Itoi Nobuki, Goto Tohiki
    Journal of Asian Ceramic Societies 7 3 361 - 367 2019年08月 [査読有り][通常論文]
  • Nagao, Masanori, Miura, Akira, Matsumoto, Ryo, Maruyama, Yuki, Watauchi, Satoshi, Takano, Yoshihiko, Tadanaga, Kiyoharu, Tanaka, Isao
    Solid State Communications 296 17 - 20 2019年07月 [査読有り][通常論文]
  • Yuwen, Hao, Goto, Yosuke, Jha, Rajveer, Miura, Akira, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Matsuda, D. Tatsuma, Aoki, Yuji, Mizuguchi, Yoshikazu
    Japanese Journal of Applied Physics 58 1 083001  2019年07月 [査読有り][通常論文]
  • Ito, Hiroaki, Miura, Akira, Goto, Yosuke, Mizuguchi, Yoshikazu, Moriyoshi,Chikako, Kuroiwa, Yoshihiro, Azuma, Masaki, Liu, Jinjia, Wen, Xiao-Dong, Nishioka,Shunta, Maeda, Kazuhiko, Masubuchi, Yuji, Rosero-Navarro, Nataly Carolina, Tadanaga, Kiyoharu
    Dalton Transactions 48 12272 - 12278 2019年06月 [査読有り][通常論文]
  • Odahara, Jin, Sun, Wenhao, Miura, Akira, Rosero-Navarro, Nataly Carolina, Masanori, Nagao, Isao, Tanaka, Ceder, Gerbrand, Tadanaga, Kiyoharu
    ACS Materials Letters 1 64 - 70 2019年06月 [査読有り][通常論文]
  • Sogabe,Ryota, Goto, Yosuke, Abe, Tomohiro, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Miura, Akira, Tadanaga, Kiyoharu, Mizuguchi, Yoshikazu
    Solid State Communications 295 43 - 49 2019年06月 [査読有り][通常論文]
  • Nagao, Masanori, Miura, Akira, Maruyama, Yuki, Watauchi, Satoshi, Takano, Yoshihiko, Tanaka, Isao
    Japanese Journal of Applied Physics 58 6 063001  2019年05月 [査読有り][通常論文]
  • Iwai, Yu, Miura, Akira, Rosero-Navarro, Nataly Carolina, Higuchi, Mikio, Tadanaga, Kiyoharu
    Journal of Asian Ceramic Societies 7 2 147 - 153 2019年05月 [査読有り][通常論文]
  • Iwai, Yu, Ikka, Takuya, Miura, Akira, Rosero-Navarro, Nataly Carolina, Iwamura, Shinichiroh, Ogino, Isao, Mukai, R. Mukai, Tadanaga, Kiyoharu
    Chemistry Letters 48 7 696 - 699 2019年04月 [査読有り][通常論文]
  • Sudo, Kenta, Goto, Yosuke, Sogabe, Ryota, Hoshi, Kazuhisa, Miura, Akira, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Mizuguchi, Yoshikazu
    Inorganic Chemistry 58 11 7628 - 7633 2019年04月 [査読有り][通常論文]
  • Miura, Akira, Rosero-Navarro, Nataly Carolina, Sakuda, Atsushi, Tadanaga, Kiyoharu, Phuc, Nguyen H. H, Matsuda, Atsunori, Machida, Nobuya, Hayashi, Akitoshi, Tatsumisago, Masahiro
    Nature Reviews Chemistry 3 189 - 198 2019年03月 [査読有り][通常論文]
     
    Solid sulfide electrolytes are key materials in all-solid-state lithium batteries because of their high lithium-ion conductivity and deformability, which enable the lithium-ion path to be connected between the material’s grain boundaries under pressure near room temperature. However, sulfur species are moisture-sensitive and exhibit high vapour pressures; therefore, syntheses of sulfide electrolytes need to be carefully designed. Liquid-phase reactions can be performed at low temperatures in controlled atmospheres, opening up the prospect of scalable processes for the preparation of sulfide electrolytes. Here, we review liquid-phase syntheses for the preparation of sulfide-based solid electrolytes and composites of electrolytes and electrodes, and we compare the charge–discharge performances of the all-solid-state lithium batteries using these components.
  • Goto, Yosuke, Miura, Akira, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Mizuguchi, Yoshikazu
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 88 2 PHYSICAL SOC JAPAN 2019年02月15日 [査読有り][通常論文]
     
    Although SbSe2-based layered compounds have been predicted to be high-performance thermoelectric materials and topological materials, most of these compounds obtained experimentally have been insulators so far. Here, we present the effect of Bi substitution on the thermoelectric properties of SbSe2-based layered compounds NdO0.8F0.2Sb1-xBixSe2 (x <= 0.4). The room temperature electrical resistivity is decreased to 8.0 x 10(-5) Omega m for x = 0.4. The electrical power factor is calculated to be 1.4 x 10(-1) W m(-1) K-2 at 660 K, which is in reasonable agreement with combined Jonker and Ioffe analysis. The room-temperature lattice thermal conductivity of less than 1 W in(-1) K-1 is almost independent of x, in contrast to the point-defect scattering model for conventional alloys. The present work provides an avenue for exploring SbSe2-based insulating and BiSe2-based conducting systems.
  • Masanori Nagao, Masashi Tanaka, Akira Miura, Miho Kitamura, Koji Horiba, Satoshi Watauchi, Yoshihiko Takano, Hiroshi Kumigashira, Isao Tanaka
    Solid State Communications 289 38 - 42 2019年02月 [査読有り][通常論文]
     
    © 2018 Elsevier Ltd Ce(O,F)Sb(S,Se)2 single crystals were successfully grown using a CsCl/KCl flux method. The obtained crystals have a plate-like shape with the typical size of 1–2 mm and well-developed ab-plane, which enables X-ray single crystal structural analysis. The Ce(O,F)Sb(S,Se)2 crystallizes in a monoclinic space group, P21/m, with lattice parameters of a = 4.121(7) Å, b = 4.109(7) Å, c = 13.233(15) Å, β = 97.94(7) °. It is composed of alternate stacking of Ce-(O,F) and Sb-SSe layers, and the Sb-SSe layer includes selective occupation of Se atoms in its in-plane site. The valence state of Ce is estimated to be Ce3+ by X-ray absorption fine spectroscopy analysis. The single crystals show an insulating behavior, and a magnetic ordering around 6 K.
  • Calpa, Marcela, Rosero-Navarro, Nataly Carolina, Miura, Akira, Kiyoharu Tadanaga
    Electrochimica Acta 296 473  2019年02月 [査読有り][通常論文]
  • Ionic conductivity of Pyrochlore-type Silver Tantalate and Fluorite-type Silver Niobate
    W. I, U. WITHANAGE, Nobuhiro Kumada, Takahiro Takei, Sayaka YANAGIDA, Kiyoharu Tadanaga, Akira Miura, Nataly Carolina Rosero-Navarro, Masaki Azuma
    J. Ceram. Soc. Jpn. in press 2019年 [査読有り][通常論文]
  • Fujii, Yuta, Miura, Akira, Rosero-Navarro, Nataly Carolina, Mizuguchi, Yoshikazu, Moriyoshi, Chikako, Kuroiwa,Yoshihiro, Higuchi, Mikio, Tadanaga, Kiyoharu
    Journal of The Electrochemical Society 165 13 A2948 - A2954 2018年11月 [査読有り][通常論文]
  • V Alexander, George, Rosero Navarro, Nataly Carolina, Miura, Akira, Tadanaga, Kiyoharu, Murugan, Ramaswamy
    Journal of Materials Chemistry A 6 21018 - 21028 2018年10月 [査読有り][通常論文]
     
    国際共同研究
  • Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Power Sources 396 31 33 - 40 2018年08月31日 [査読有り][通常論文]
     
    All-solid-state lithium batteries based on sulfide solid electrolytes are potential candidates for large-scale energy storage applications. Here, composite cathode with high content of an active material was prepared by a liquid phase process assisted by a dispersant agent to produce a better electrode and electrolyte interface. Li6PS5Cl sulfide electrolyte derived from a solution containing dispersant showed an argyrodite crystal phase with a better distribution of particle size and higher conductivity compared with those without dispersant. Regular distribution of Li6PS5Cl particles in nanometric scale with a spherical shape below 500 nm and conductivity of 0.6 × 10−3 S cm−1 (ρ = 1.40 g cm−3) at room temperature were obtained. Composite cathode was prepared by the dispersion of LiNi1/3Mn1/3Co1/3O2 particles and carbon additive in the Li6PS5Cl-solution containing dispersant agent and subsequent drying at 180 °C. Bulk-type all-solid-state battery fabricated with the composite cathode containing 89 wt% of the active material showed an initial discharge capacity of 110 mA h g−1 at 25 °C and maintained 95% discharge capacity after 15 cycles.
  • Goto, Yosuke, Miura, Akira, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Matsuda, Tatsuma D, Aoki, Yuji, Mizuguchi, Yoshikazu
    SCIENTIFIC REPORTS 8 NATURE PUBLISHING GROUP 2018年08月27日 [査読有り][通常論文]
     
    Superconductors with a van der Waals (vdW) structure have attracted a considerable interest because of the possibility for truly two-dimensional (2D) superconducting systems. We recently reported NaSn2As2 as a novel vdW-type superconductor with transition temperature (T-c) of 1.3 K. Herein, we present the crystal structure and superconductivity of new material Na1-xSn2P2 with T-c = 2.0 K. Its crystal structure consists of two layers of a buckled honeycomb network of SnP, bound by the vdW forces and separated by Na ions, as similar to that of NaSn2As2. Amount of Na deficiency (x) was estimated to be 0.074(18) using synchrotron X-ray diffraction. Bulk nature of superconductivity was confirmed by the measurements of electrical resistivity, magnetic susceptibility, and specific heat. First-principles calculation using density functional theory shows that Na1-xSn2P2 and NaSn2As2 have comparable electronic structure, suggesting higher Tc of Na1-xSn2P2 resulted from increased density of states at the Fermi level due to Na deficiency. Because there are various structural analogues with tin-pnictide (SnPn) conducting layers, our results indicate that SnPn-based layered compounds can be cate
  • Rosero-Navarro, Nataly Carolina, Miura, Akira, Kiyoharu Tadanaga
    Journal of Sol-Gel Science and Technology 89 1 303 - 309 2018年08月 [査読有り][通常論文]
  • Takahashia, Natsuumi, Nagao, Masanori, Miura, Akira, Watauchi, Satoshi, Tadanaga, Kiyoharu, Yoshikiko Takano, Tanaka, Isao
    Journal of the Ceramics Society Japan 126 7 591 - 593 2018年07月 [査読有り][通常論文]
  • Hirai, Shigeto, Morita, Kazuki, Yasuoka, Kenji, Shibuya, Taizo, Tojo, Yujiro, Kamihara, Yoichi, Miura, Akira, Suzuki, Hisao, Ohno, Tomoya, Matsuda, Takeshi, Yagi, Shunsuke
    Journal of Materials Chemistry A 6 31 15102 - 15109 2018年07月 [査読有り][通常論文]
  • Moe Narita, Mikio Higuchi, Takayo Ogawa, Satoshi Wada, Akira Miura, Kiyoharu Tadanaga
    Optical Materials 80 57 - 61 2018年06月01日 [査読有り][通常論文]
     
    Yb:CaYAlO4 single crystals were grown by the floating zone method and their spectral properties were investigated. Void formation was effectively suppressed by using a feed rod of Y-rich composition with the aid of a double zone-pass technique. For the oxygen excess composition of Yb:Ca0.9925Y1.0075AlO4.00375, a void-free crystal was obtained by performing only the double zone-pass. On the other hand, for cation-deficient type of Yb:Ca0.9925Y1.005AlO4, void-free crystal could not be obtained by performing the double zone-pass. The void formation is attributable to the constitutional supercooling caused by segregation of main constituents of Y and Ca, and the congruent composition may exist in the Y-rich region with existence of interstitial excess oxide ions. The absorption cross section for σ-polarization was slightly larger than that for π-polarization, which is reasonable on the basis of the crystal structure of CaYAlO4.
  • Takahashia, Natsuumi, Ito, Hiroaki, Miura, Akira, Rosero-Navarro, Nataly Carolina, Goto, Yosuke, Mizuguchi, Yoshikazu, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Nagao, Masanori, Watauchi, Satoshi, Tanaka, Isao, Tadanaga, Kiyoharu
    Journal of Alloys and Compounds 750 25 409 - 413 2018年06月 [査読有り][通常論文]
  • Akira Miura, Masanori Nagao, Yosuke Goto, Yoshikazu Mizuguchi, Tatsuma D. Matsuda, Yuji Aoki, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yoshihiko Takano, Satoshi Watauchi, Isao Tanaka, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga
    Inorganic Chemistry 57 9 5364 - 5370 2018年05月07日 [査読有り][通常論文]
     
    Ce1-xPrxOBiS2 powders and Ce0.5Pr0.5OBiS2 single crystals were synthesized and their structure and superconductive properties were examined by X-ray diffraction, X-ray absorption, electronic resistivity, and magnetization. While PrOBiS2 was found to be in a monoclinic phase with one-dimensional Bi-S zigzag chains showing no superconductive transition above 0.1 K, CeOBiS2 was in a tetragonal phase with two-dimensional Bi-S planes showing zero resistivity below 1.3 K. In the range x = 0.3-0.9 in Ce1-xPrxOBiS2, both monoclinic and tetragonal phases were formed together with zero resistivity up to a maximum temperature of 2.2 K. A Ce0.5Pr0.5OBiS2 single crystal, which showed both zero resistivity and a decrease in magnetization at ∼2.4 K, presented a tetragonal structure. Short Bi-S bonding in flat two-dimensional Bi-S planes and mixed Ce3+/Ce4+ were characteristic features of the Ce0.5Pr0.5OBiS2 single crystal, which presumably triggered its superconductivity.
  • Daniel Ramirez, Yusaku Suto, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga, Franklin Jaramillo
    Inorganic Chemistry 57 7 4181 - 4188 2018年04月02日 [査読有り][通常論文]
     
    Organic-inorganic hybrid perovskite materials have recently been investigated in a variety of applications, including solar cells, light emitting devices (LEDs), and lasers because of their impressive semiconductor properties. Nevertheless, the perovskite structure has the ability to host extrinsic elements, making its application in the battery field possible. During the present study, we fabricated and investigated the electrochemical properties of three-dimensional (3D) methylammonium lead mixed-halide CH3NH3PbI3-xBrx and two-dimensional (2D) propylammonium-methlylammonium lead bromide (CH3NH3)2(CH3(CH2)2NH3)2Pb3Br10 hybrid perovskite thin films as electrode materials for Li-ion batteries. These electrodes were obtained by solution processing at 100 °C. CH3NH3PbBr3 achieved high discharge/charge capacities of ∼500 mA h g-1 /160 mA h g-1 that could account also for other processes taking place during the Li intercalation. It was also found that bromine plays an important role for lithium intercalation, while the new 2D (CH3NH3)2(CH3(CH2)2NH3)2Pb3Br10 with a layered structure allowed reversibility of the lithium insertion-extraction of 100% with capacities of ∼375 mA h g-1 in the form of a thin film. Results suggest that tuning the composition of these materials can be used to improve intercalation capacities, while modification from 3D to 2D layered structures contributes to improving lithium extraction. The mechanism of the lithium insertion-extraction may consist of an intercalation mechanism in the hybrid material accompanying the alloying-dealloying process of the LixPb intermetallic compounds. This work contributes to revealing the relevance of both composition and structure of potential hybrid perovskite materials as future thin film electrode materials with high capacity and compositional versatility.
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Inorganic Chemistry Frontiers 5 2 501 - 508 2018年02月01日 [査読有り][通常論文]
     
    Sulfide solid electrolytes in the Li2S-P2S5 system were synthesized by a liquid phase process under ultrasonic irradiation, and heat treatments at low temperatures. Crystal phase, structure, morphology and ionic conductivity of the sulfide electrolytes were examined after solvent removal at 180 °C and two different heat treatment temperatures, 220 °C and 250 °C. The study revealed that the ionic conductivities of the xLi2S·(100 - x)P2S5 sulfide electrolytes, in compositions with 70 ≤ x ≤ 75 mol%, are largely influenced by the local structure. The heat treatment at 220 °C was found to be an adequate temperature to promote crystallization of the high ionic conductive Li7P3S11 phase. Higher temperatures for heat treatment such as 250 °C lead to the formation of P2S6 4- (hypo-thiodiphosphate) units in the local structure of the sulfide electrolytes leading to a reduction of ionic conductivity. The formation and distribution of PS4 3- (ortho-thiophosphate), P2S7 4- (pyro-thiophosphate) and P2S6 4- units in the local structure were found to be key factors in achieving higher ionic conductivity (up to 10-3-10-4 S cm-1 at room temperature).
  • Jin Odahara, Akira Miura, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga
    Inorganic Chemistry 57 1 24 - 27 2018年01月02日 [査読有り][通常論文]
     
    An intense exothermic and explosive reaction between Ba(OH)2, NbCl5, and NaNH2 produced barium niobium perovskite oxynitride in seconds. The addition of hexane reduced the risk of explosion during mixing of the starting materials, and subsequent heat treatment at 498 K in hexane allowed control of this exothermic reaction, leading to formation of the perovskite oxynitride with fewer impurities. The synthesis of barium tantalum perovskite oxynitride under similar reaction conditions was successful.
  • Yosuke Goto, Akira Miura, Ryosuke Sakagami, Yoichi Kamihara, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yoshikazu Mizuguchi
    Journal of the Physical Society of Japan 87 7 074703  2018年 [査読有り][通常論文]
     
    Inspired by the recent first-principles calculations showing the high thermoelectric performance of layered pnictogen chalcogenides, we experimentally characterise the crystal structure and high-temperature transport properties of the layered antimony selenides REOSbSe2 (RE = La, Ce). The crystal structure of REOSbSe2 was the tetragonal P4=nmm space group, consisting of alternate stacks of SbSe2 and REO layers. These two compounds were n-type semiconductors. The optical band gaps of LaOSbSe2 and CeOSbSe2 were evaluated to be 1.0 and 0.6 eV, respectively. The room-temperature thermal conductivity was 1.5 W m−1 K−1 for RE = La and 0.8 W m−1 K−1 for RE = Ce. These relatively low thermal conductivities were comparable to those of isostructural layered bismuth chalcogenides. We substituted O2− with F− ions to introduce electrons as charged carriers to optimize the thermoelectric performance, but increasing the electrical conductivity was still challenging.
  • Y. Goto, A. Nishida, H. Nishiate, M. Murata, C. H. Lee, A. Miura, C. Moriyoshi, Y. Kuroiwa, Y. Mizuguchi
    Dalton Transactions 47 8 2575 - 2580 2018年 [査読有り][通常論文]
     
    Silver bismuth diselenide (AgBiSe2) has attracted much attention as an efficient thermoelectric material, owing to its intrinsically low lattice thermal conductivity. While samples synthesized using a solid-state reaction showed n-type conductivity and their dimensionless figure of merit (ZT) reached ∼1 by electron doping, theoretical calculations predicted that a remarkably high thermoelectric performance can be achieved in p-type AgBiSe2. In this paper, we present the effect of Te substitution on the crystal structure and thermoelectric properties of AgBiSe2, expecting p-type conductivity due to the shallowing of the energy potential of the valence band. We found that all AgBiSe2-xTex (x = 0-0.8) prepared using a solid-state reaction exhibits n-type conductivity from 300 to 750 K. The room-temperature lattice thermal conductivity decreased to as low as 0.3 W m-1 K-1 by Te substitution, which was qualitatively described using the point defect scattering model for the solid solution. We show that ZT reaches ∼0.6 for x = 0.8 at a broad range of temperatures, from 550 to 750 K, due to the increased power factor, although the carrier concentration has not been optimized yet.
  • Yoshikazu Mizuguchi, Kazuhisa Hoshi, Yosuke Goto, Akira Miura, Kiyoharu Tadanaga, Chikako Moriyoshi, Yoshihiro Kuroiwa
    Journal of the Physical Society of Japan 87 2 023704  2018年 [査読有り][通常論文]
     
    In order to understand the mechanisms behind the emergence of superconductivity by the chemical pressure effect in REO0.5F0.5BiS2 (RE = La, Ce, Pr, and Nd), where bulk superconductivity is induced by the substitutions with a smaller-radius RE, we performed synchrotron powder X-ray diffraction, and analyzed the crystal structure and anisotropic displacement parameters. With the decrease of the RE3+ ionic radius, the in-plane disorder of the S1 sites significantly decreased, very similar to the trend observed in the Se-substituted systems: LaO0.5F0.5BiS2−xSex and Eu0.5La0.5FBiS2−xSex. Therefore, the emergence of bulk superconductivity upon the suppression of the in-plane disorder at the chalcogen sites is a universal scenario for the BiCh2-based superconductors. In addition, we indicated that the amplitude of vibration along the c-axis of the in-plane chalcogen sites may be related to the Tc in the BiCh2-based superconductors.
  • Shunjiro Chida, Akira Miura, Nataly Carolina Rosero-Navarro, Mikio Higuchi, Nguyen H. H. Phuc, Hiroyuki Muto, Atsunori Matsuda, Kiyoharu Tadanaga
    CERAMICS INTERNATIONAL 44 1 742 - 746 2018年01月 [査読有り][通常論文]
     
    Lithium-ion conductive Li6PS5Br is prepared using ultrasonication of Li2S, P2S5 and LiBr in ethyl propionate-ethanol solution and subsequent heating at 453 K. The main phase of the synthesized product is Li6PS5Br and its lithium ion conductivity is 3.4 x 10(-5) S cm(-1) at room temperature. The cathode composite of LiCo1/3Ni1/3Mn1/3O2, Li6PS5Br and vapor grown carbon fiber (VGCF) is prepared via ultrasonication of the Li6PS5Br precursor solution containing LiCo1/3Ni1/3Mn1/3O2 and VGCF, and the all-solid-state lithium battery using this cathode composite is fabricated. The cell exhibits the discharge capacity of 109 mAh g(-1) for the first cycle and its capacity of 87 mAh g(-1) after 10 cycles.
  • Yudai Hijikata, Tomohiro Abe, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yosuke Goto, Akira Miura, Kiyoharu Tadanaga, Yongming Wang, Osuke Miura, Yoshikazu Mizuguchi
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 12 124802  2017年12月 [査読有り][通常論文]
     
    We have synthesized a new layered oxychalcogenide La2O2Bi3AgS6. From synchrotron X-ray diffraction and Rietveld refinement, the crystal structure of La2O2Bi3AgS6 was refined using a model of the P4/nmm space group with a = 4.0644(1) angstrom' and c = 19.412(1) angstrom, which is similar to the related compound LaOBiPbS3, while the interlayer bonds (M2-S1 bonds) are apparently shorter in La2O2Bi3AgS6. The tunneling electron microscopy (TEM) image confirmed the lattice constant derived from Rietveld refinement (c similar to 20 angstrom). The electrical resistivity and Seebeck coefficient suggested that the electronic states of La2O2Bi3AgS6 are more metallic than those of LaOBiS2 and LaOBiPbS3. The insertion of a rock-salt-type chalcogenide into the van der Waals gap of BiS2-based layered compounds, such as LaOBiS2, will be a useful strategy for designing new layered functional materials in the layered chalcogenide family.
  • Anongsack Paseuth, Yasuki Kido, Shinya Imamura, Kazuo Yamagata, Akira Miura, Kiyoharu Tadanaga
    Journal of the Ceramic Society of Japan 125 12 913 - 918 2017年12月01日 [査読有り][通常論文]
     
    Al-rich cubic (c-) AlxTi1-xN (x μ 0.8) coating comprising self-organised c-Al(Ti)N/c-Ti(Al)N nanolamellae was prepared in a previous study by low-pressure chemical vapour deposition (LP-CVD) using an AlCl3-TiCl4-NH3-Ar-H2 precursor system. In the present study, we investigated the effects of isothermal annealing at 800 to 1200°C for 1 to 10 h on the crystal structure, microstructure, and hardness of the coating, and compared them to those of a monolithic c-AlxTi1-xN (x μ 0.6) coatings prepared by arc-evaporated physical vapour deposition (PVD). The X-ray diffraction patterns indicated high phase stability of the former coating up to 1200°C after 1 h. High-resolution transmission electron microscopy revealed that the nanolamellae in c-AlxTi1-xN (x μ 0.8) coating remained stable after post-annealing at 900°C for 5 h. The spontaneously formed coherent nanostructure suppressed diffusion in this coating, and the spinodal decomposition and hexagonal phase formation were thus shifted to higher temperatures. Consequently, age hardening in LP-CVD c-AlxTi1-xN (x μ 0.8) helped to maintain its hardness at up to 1100°C after 10 h. The improved thermal stability and hardness at elevated temperature of the Al-rich c-AlxTi1-xN coating by LP-CVD led to a significant improvement in the cutting tool life, by factors of 2 and 10 compared to state-of-the-art CVD-and PVD-coated inserts, respectively. These improvements in thermal stability and elevated hardness in c-AlxTi1-xN (x μ 0.8) coating prepared via LP-CVD process could remarkably enhance tool life for dry and high-speed cutting applications.
  • Kumada, Nobuhiro, Koike, Narumi, Nakanome, Kousuke, Yanagida, Sayaka, Takei, Takahiro, Miura, Akira, Magome, Eisuke, Moriyoshi, Chikako, Kuroiwa, Yoshihiro
    Journal of Asian Ceramic Societies 5 3 284 - 289 2017年09月01日 [査読有り][通常論文]
     
    Rutile-type solid solutions Ni1−xCoxTi(Nb1−yTay)2O8 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) were prepared by high temperature solid state reaction. The solid solutions of noibates (y = 0) had a rutile-type structure and those of tantalates (y = 1.0) had a trirutile-type one. The trirutile-type structure appeared in the composition of y ≥ 0.4. The crystal structures of these solid solutions for niobates and tantalates were refined by using synchrotron X-ray powder diffraction data and the R-factors were Rwp = 1.76–1.92% and Rp = 1.13–1.19% for niobates and Rwp = 10.3–12.2% and Rp = 6.78–9.14% for tantalates. Their lattice parameters for noibates ranges from a = 4.69413(2) to 4.70411(2) Å and c = 3.02187(1) to 3.03242(1) Å and those for tantalates ranges from a = 4.6946(2) to 4.7065(2) Å and c = 9.0829(3) to 9.1164(4) Å. The optical band gap for these solid solutions ranged from 1.63 to 2.50 eV and only NiTiTa2O8 exhibited photocatalytic activity for phenol decomposition under UV light irradiation. The dielectric constants for four end members, NiTiNb2O8, CoTiNb2O8, NiTiTa2O8 and CoTiTa2O8 were 25–75 in the temperature range from room temperature to 300 °C.
  • Akira Miura, Tsukasa Hokimoto, Masanori Nagao, Takashi Yanase, Toshihiro Shimada, Kiyoharu Tadanaga
    ACS omega 2 8 5271 - 5282 2017年08月31日 [査読有り][通常論文]
     
    The relationship of liquidus temperatures among six binary and four ternary phases in a Ag-Al-Sn-Zn system was analyzed by means of statistical modeling. Four statistical models to predict changes in the liquidus temperatures in Ag-Al-Sn-Zn were proposed on the basis of different hypotheses derived from macroscopic and microscopic standpoints. The results of interpolation tests to evaluate the prediction accuracies of the ternary liquidus temperatures suggested that the multivariate regression model based on binary liquidus temperatures, interactive binary liquidus temperatures, and products of atomic ratios was found to be the most effective among the four models. It was numerically shown that the prediction accuracies of the liquidus temperatures in local ternary systems of Ag-Al-Sn-Zn can be improved further by using the models identified in their neighboring systems. Finally, the possibility to extract the general trend and the abnormal combination of elements for the prediction of liquidus temperatures was discussed on the basis of the statistical framework we considered.
  • Y. Mizuguchi, Y. Hijikata, T. Abe, C. Moriyoshi, Y. Kuroiwa, Y. Goto, A. Miura, S. Lee, S. Torii, T. Kamiyama, C. H. Lee, M. Ochi, K. Kuroki
    EPL 119 2 26002  2017年07月 [査読有り][通常論文]
     
    We have investigated the crystal structure of LaOBiPbS3 using neutron diffraction and synchrotron X-ray diffraction. From structural refinements, we found that the two metal sites, occupied by Bi and Pb, were differently surrounded by the sulfur atoms. Calculated bond valence sum suggested that one metal site was nearly trivalent and the other was nearly divalent. Neutron diffraction also revealed site selectivity of Bi and Pb in the LaOBiPbS3 structure. These results suggested that the crystal structure of LaOBiPbS3 can be regarded as alternate stacks of the rock-salt-type Pb-rich sulfide layers and the LaOBiS2-type Bi-rich layers. From band calculations for an ideal (LaOBiS2)(PbS) system, we found that the S bands of the PbS layer were hybridized with the Bi bands of the BiS plane at around the Fermi energy, which resulted in the electronic characteristics different from that of LaOBiS2. Stacking the rock-salt type sulfide (chalcogenide) layers and the BiS2-based layered structure could be a new strategy to exploration of new BiS2-based layered compounds, exotic two-dimensional electronic states, or novel functionality. Copyright (C) EPLA, 2017
  • Akira Miura, Takayoshi Oshima, Kazuhiko Maeda, Yoshikazu Mizuguchi, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yu Meng, Xiao-Dong Wen, Masanori Nagao, Mikio Higuchia, Kiyoharu Tadanaga
    JOURNAL OF MATERIALS CHEMISTRY A 5 27 14270 - 14277 2017年07月 [査読有り][通常論文]
     
    Indium oxychalcogenides would be attractive semiconductors considering the practical use of indium oxides and sulfides such as indium-tin oxides (ITO) and copper-indium-gallium diselenides (CIGS). In this work, a novel layered indium oxysulfide, LaOInS2, was synthesized by a metathesis reaction between LaOCl and NaInS2. Synchrotron X-ray diffraction showed that LaOInS2 consisted of alternately stacked rocksalt-type In-S and PbO-type La-O layers. The InS6 octahedron had split In sites with abnormally large anisotropic atomic displacement factors. LaOInS2 was found to be a direct semiconductor. Density functional theory calculations exhibited well-dispersed bands composed of In 5s/5p and S 3p/O 2p orbitals with a band gap of similar to 2.4 eV, which was close to the experimental value estimated by optical absorption (2.64 eV). Under visible light irradiation this visible-light absorption, LaOInS2 exhibited photocatalytic activity for H-2 and O-2 evolution from water with the aid of Pt and IrO2 cocatalysts, respectively.
  • Kouhei Nagasaka, Atsuhiro Nishida, Rajveer Jha, Joe Kajitani, Osuke Miura, Ryuji Higashinaka, Tatsuma D. Matsuda, Yuji Aoki, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Hidetomo Usui, Kazuhiko Kuroki, Yoshikazu Mizuguchi
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 7 074701  2017年07月 [査読有り][通常論文]
     
    We have investigated the crystal structure and physical properties of LaO1-xFxBiSSe to reveal the intrinsic superconductivity phase diagram of the BiCh2-based layered compound family. From synchrotron X-ray diffraction and Rietveld refinements with anisotropic displacement parameters, we clearly found that the in-plane disorder in the BiSSe layer was fully suppressed for all x. In LaO1-xFxBiSSe, metallic conductivity and superconductivity are suddenly induced by electron doping even at x = 0.05 and 0.1 with a monoclinic structure. In addition, x (F concentration) dependence of the transition temperature (T-c) for x = 0.2 -0.5 with a tetragonal structure shows an anomalously flat phase diagram. With these experimental facts, we have proposed the intrinsic phase diagram of the ideal BiCh(2)-based superconductors with less in-plane disorder.
  • Yuta Fujii, Akira Miura, Nataly Carolina Rosero-Navarro, Mikio Higuchi, Kiyoharu Tadanaga
    ELECTROCHIMICA ACTA 241 1 370 - 374 2017年07月 [査読有り][通常論文]
     
    In bulk-type all-solid-state lithium batteries with sulfide-based solid electrolytes, composite electrodes, in which an active material, a solid electrolyte, and a conductive additive are mixed, have been used to enhance lithium-ion diffusion and electronic conductivity. However, the addition of electrolytes and electron-conductive additives to the composite electrodes decreases the amount of active materials in the batteries. In the present study, FePS3 was employed as the electrode in an all-solid-state lithium secondary battery, without mixing the solid electrolytes and conductive additives. The all-solid-state cell using the FePS3 electrode exhibited reversible charge-discharge behavior for more than 30 cycles under a constant current density of 0.13 mA cm (2) at room temperature. The discharge capacity of the cell was 107 mAh g (1) at the 30th cycle. This behavior was comparable to that of a cell with an electrode including a solid electrolyte and/or a conductive additive, indicating that the FePS3 electrode had sufficient paths of lithium ions and of electron conduction. These results suggest that FePS3 is an attractive iron-based electrode for an all-solid-state battery using a sulfide-based solid electrolyte. (C) 2017 Elsevier Ltd. All rights reserved.
  • Akira Miura, Satoshi Ishii, Masanori Nagao, Ryo Matsumoto, Yoshihiko Takano, Satoshi Watauchi, Isao Tanaka, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga
    Journal of Asian Ceramic Societies 5 2 183 - 185 2017年06月01日 [査読有り][通常論文]
     
    LaO0.5F0.5BiS2 nanosheets were produced by ultrasonification. A slightly reddish colloidal suspension was obtained by ultrasonification of LaO0.5F0.5BiS2 powder in ethanol. Transmission electron microscope (TEM) images of the dried suspension indicated the nanosheet morphology of LaO0.5F0.5BiS2, and the electron diffraction spots indicated 4-fold symmetry. The thickness of the sheets was 2–6 nm, which corresponded to 2–4 unit cells of the c-axis of LaO0.5F0.5BiS2.
  • Nataly Carolina Rosero-Navarro, Taiki Kinoshita, Akira Miura, Mikio Higuchi, Kiyoharu Tadanaga
    IONICS 23 6 1619 - 1624 2017年06月 [査読有り][通常論文]
     
    All-solid-state batteries with cathode composites containing high concentration of active materials are required to achieve higher energy densities. Here, a composite cathode containing up to 89 wt% of high-voltage cathode active material (LiNi1/3Mn1/3Co1/3O2) was prepared by covering this with a solution-derived solid electrolyte (argyrodite, Li6PS5Cl) and the incorporation of different content binder (ethyl cellulose). All-solid-state batteries were fabricated using 80Li(2)Sa (TM) 20P(2)S(5) (mol%) glass and indium metal as a solid electrolyte and anode, respectively. The all-solid-state battery with a composite cathode containing 0.5 wt% of ethyl cellulose showed an initial discharge capacity of 45 mAhg(-1) at 25 A degrees C and maintained 91.7% of the discharge capacity after ten cycles, around 30% higher than that obtained for the battery with the composite cathode without a binder.
  • Yudai Hijikata, Atsuhiro Nishida, Kohei Nagasaka, Osuke Miura, Akira Miura, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yoshikazu Mizuguchi
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 5 054711  2017年05月 [査読有り][通常論文]
     
    We have synthesized AgSn1-xBixSe2 polycrystalline samples to investigate the effect of partial substitution of mixed-valence Sn by Bi3+ to the superconductivity of the valence-skip superconductor AgSnSe2. The Bi-substituted AgSn1-x-BixSe2 were obtained up to x = 0.2, but an insulating phase Ag2SnBi2Se5 with a NaCl-type structure showed up above x = 0.3. The superconducting transition temperature increased from 4.5K (x = 0) to 5.0K (x = 0.1) by Bi substitution. The enhancement of superconductivity by the suppression of the valence-skip states of Sn suggests that the valence-skip states of Sn are not positively linked to the pairing mechanisms of superconductivity in the AgSnSe2 system.
  • Yu Su, Yoshihiro Tsujimoto, Akira Miura, Shinichiro Asai, Maxim Avdeev, Hiraku Ogino, Miho Ako, Alexei A. Belik, Takatsugu Masuda, Tetsuo Uchikoshi, Kazunari Yamaura
    CHEMICAL COMMUNICATIONS 53 27 3826 - 3829 2017年04月 [査読有り][通常論文]
     
    A new square-planar zinc oxyhalide, Sr2ZnO2Cl2, was successfully synthesized using a high-pressure method. Absorption spectroscopy revealed an indirect band gap of 3.66 eV. Electronic structure calculations indicated a strong hybridization between Zn 3d(x2-y2) and O 2p orbitals, which is distinct from tetrahedrally coordinated ZnO.
  • Rubel, Mirza HK, Takei, Takahiro, Kumada, Nobuhiro, Mozahar, Ali M, Miura, Akira, Tadanaga, Kiyoharu, Oka, Kengo, Azuma, Masaki, Magomae, Eisuke, Moriyoshi, Chikako, Kuroiwa, Yoshihiro
    Inorganic Chemistry 56 6 3174 - 3181 2017年03月 [査読有り][通常論文]
     
    We have synthesized a new superconducting perovskite bismuth oxide by a facile hydrothermal route at 220 degrees C. The choice of starting materials, their mixing ratios, and the hydrothermal reaction temperature was crucial for obtaining products with superior superconducting properties. The structure of the powder sample was investigated using laboratory X-ray diffraction, high -resolution synchrotron X-ray diffraction (SXRD) data, and electron diffraction (ED) patterns [transmission electron microscopy (TEM) analysis]. The refinement of SXRD data confirmed a simple perovskitetype structure with a cubic cell of a = 4.27864(2) angstrom [space group Pm3m (No. 221)]. Elemental analysis detected magnesium in the final products, and a refinement based on SXRD and inductively coupled plasma data yielded an ideal undistorted simple cubic perovskite-type structure, with the chemical composition (Ba0.62K0.38)(Bi0.92Mg0.08)O-3. ED patterns also confirmed the simple cubic perovskite structure; the cube -shaped microstructures and compositional homogeneity on the nanoscale were verified by scanning electron microscopy and TEM analyses, respectively. The fabricated compound exhibited a large shielding volume fraction of about 98% with a maximum T-c(mag) of similar to 30 K, which was supported by the measured bismuth valence as well. Its electrical resistivity dropped at similar to 21 K, and zero resistivity was observed below 7 K The compound underwent thermal decomposition above 400 degrees C. Finally, the calculated band structure showed a metallic behavior for this hydrothermally synthesized bismuth oxide.
  • Fumitake Okabe, Chinami Mochizuki, Takahiro Takei, Sayaka Yanagida, Akira Miura, Nobuhiro Kumada
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 10 732 - 736 2017年 [査読有り][通常論文]
     
    Mesoporous silica-phosphate hybrids were successfully prepared by three processes: hybridization post synthesis by H3PO4, hybridizations during synthesis by Na2HPO4 and by PO(OC2H5). X-ray diffraction patterns confirm that the hexagonal pore structure was maintained after the hybridization process. The maximum phosphate amount was 2.9 mol% in the sample prepared by hybridization during synthesis from Na2SiO3 and PO(OC2H5)(3). The specific surface area showed a large value of approximately 1000 m(2)/g despite the hybridization. The Si-O-P bonds were confirmed by nuclear magnetic resonance and X-ray photoelectron spectroscopy. The maximum adsorption amount of rare earth metal cations into the hybrid was approximately 70% of the initial concentration (50 mg/L) for each rare earth metal cation in coexistence with 13 rare earth metal cations. (C) 2017 The Ceramic Society of Japan. All rights reserved.
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    RSC ADVANCES 7 73 46499 - 46504 2017年 [査読有り][通常論文]
     
    A solid electrolyte with a small particle size, good mechanical properties and high ionic conductivity is required to achieve high energy and power density in the all-solid-state battery. Here, we report an instantaneous preparation of high lithium-ion conducting sulfide solid electrolyte Li7P3S11 by a simple procedure involving a liquid phase process under ultrasonic irradiation and low thermal treatment at 220 degrees C. A short reaction time of 30 min was enough to produce the formation of PS43- units. Subsequent drying and heating processes led to the precipitation of the Li7P3S11 phase with a particle size below 500 nm, achieving high ionic conductivity of 1.0 x 10(-3) S cm(-1) at 22 degrees C and a low activation energy of 12.8 kJ mol(-1).
  • Akira Miura
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 7 552 - 558 2017年 [査読有り][招待有り]
     
    Nitrides and oxynitrides exhibit great potential for novel material development, since their electronic structures can be controlled by tuning the amounts of air-abundant nitrogen and oxygen elements therein. However, the above control methods still need to be developed, and the crystal and electronic structures of the produced nitrides/oxynitrides need to be understood. Herein, I summarize the recent progress in nitride and oxynitride synthesis, highlighting novel low-temperature nitridation of oxides by molten NaNH2, and attempt to rationalize the crystal and electronic structures of nitride and oxynitrides. Moreover, I describe how the catalytic activity of manganese oxynitrides in the oxygen reduction reaction can be enhanced by tuning their nitrogen content and thus their electronic structures. (C)2017 The Ceramic Society of Japan. All rights reserved.
  • Nobuhiro Kumada, Ayumi Nakamura, Akira Miura, Takahiro Takei, Masaki Azuma, Hajime Yamamoto, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa
    JOURNAL OF SOLID STATE CHEMISTRY 245 30 - 33 2017年01月 [査読有り][通常論文]
     
    A new lithium copper bismuth oxide, LiCuBiO4 was prepared by hydrothermal reaction using NaBiO3.1.4H(2)O. The crystal structural model of this compound was refined by using synchrotron X-ray powder diffraction data. This bismuthate has the LiCuSbO4 related structure with the orthorhombic cell (Space group: Pnma) of a=10.9096(9), b=5.8113(5) and c=5.0073(4) angstrom, and the final R-factors were R-factors were R-wp=4.84 and R-p=3.58%. This compound is the first example of a lithium copper bismuthate containing Bi5+ An antiferromagnetic ordering of Cu2+ moment was observed at 6 K.
  • Paseuth, Anongsack, Yamagata, Kazuo, Miura, Akira, Higuchi, Mikio, Tadanaga, Kiyoharu
    Journal of the American Ceramic Society 100 1 343 - 353 2017年01月 [査読有り][通常論文]
     
    Metastable c-AlxT1-xN is an important and well-established hard coating in the tool industry. To improve the mechanical and thermal properties, Al-rich c-AlxTi1-xN coatings with controllable preferred crystal orientations were fabricated via low-pressure chemical vapor deposition (LP-CVD) in an industrial plant, using an AlCl3-TiCl4-NH3-Ar-H-2 precursor system. The c-AlxTi1-xN coatings with (100)- and (111)-preferred orientations and average x values of 0.82 and 0.73, respectively, comprised c-Al(Ti)N/c-Ti(Al)N nanolamellae with average compositions of c-Al0.9Ti0.1N/c-Al0.6Ti0.4N and c-Al0.80Ti0.20N/c-Al0.50Ti0.50N; the average lamellar periods were 7.7 and 4.5 nm, respectively. High-resolution transmission electron microscopy indicated that the c-Al(Ti)N/c-Ti(Al)N nanolamellae were modulated along the < 100 > direction, implying coherent spinodal decomposition of c-AlxTi1-xN in the as-deposited state. The hardness of the c-AlxTi1-xN coatings varied from 33 to 36 GPa, depending on the (100)- or (111)-preferred orientation. Residual stress measurements in the as-deposited state showed tensile stress values of 1.8 and 4.6 GPa for the (100)- and (111)-oriented c-AlxT1-xN coatings, respectively. This stress may be generated by the difference in the thermal expansion coefficient of the c-AlxT1-xN coating and the carbide substrate and by coherency stress in the c-Al(Ti)N/c-Ti(Al)N nanolamellae. In situ high-temperature X-Ray diffraction results revealed high thermal stability up to 1000 degrees C.
  • Rosero-Navarro, Nataly Carolina, Yamashita, Taira, Miura, Akira, Higuchi, Mikio, Tadanaga, Kiyoharu
    Journal of the American Ceramic Society 100 1 276 - 285 2017年01月 [査読有り][通常論文]
     
    Lithium ion conductors with garnet-type structure are promising candidates for applications in all solid-state lithium ion batteries, because these materials present a high chemical stability against Li metal and a rather high Li+ conductivity (10(-3)-10(-4)S/cm). Producing densified Li-ion conductors by lowering sintering temperature is an important issue, which can achieve high Li conductivity in garnet oxide by preventing the evaporation of lithium and a good Li-ion conduction in grain boundary between garnet oxides. In this study, we concentrate on the use of sintering additives to enhance densification and microstructure of Li7La3ZrNbO12 at sintering temperature of 900 degrees C. Glasses in the LiO2-B2O3-SiO2-CaO-Al2O3 (LBSCA) and BaO-B2O3-SiO2-CaO-Al2O3 (BBSCA) system with low softening temperature (<700 degrees C) were used to modify the grain-boundary resistance during sintering process. Lithium compounds with low melting point (<850 degrees C) such as LiF, Li2CO3, and LiOH were also studied to improve the rearrangement of grains during the initial and middle stages of sintering. Among these sintering additives, LBSCA and BBSCA were proved to be better sintering additives at reducing the porosity of the pellets and improving connectivity between the grains. Glass additives produced relative densities of 85-92%, whereas those of lithium compounds were 62-77%. Li7La3ZrNbO12 sintered with 4 wt% of LBSCA at 900 degrees C for 10h achieved a rather high relative density of 85% and total Li-ion conductivity of 0.8x10(-4)S/cm at room temperature (30 degrees C).
  • Rosero-Navarro, Nataly Carolina, Miura, Akira, Higuchi, Mikio, Tadanaga, Kiyoharu
    Journal of Electronic Materials 46 1 497 - 501 2017年01月 [査読有り][通常論文]
     
    Simultaneous effect of Al2O3 and Li3BO3 additions on sintering behavior and Li-ion conductivity of Li7-xLa2.95Ca0.05ZrTaO12 (LLCZT) garnet electrolyte sintered at 900 degrees C (10 h) is evaluated. The crystal phase and microstructure of the different composites were evaluated by x-ray diffraction and scanning electron microscopy (SEM), respectively. Electrical properties of the composites with high relative densities (95%) were examined by impedance spectroscopy. The cubic phase was formed for LLCZT sintered with 0-0.21 mol of Al2O3 and 0.70 mol-0.80 mol of Li3BO3. The excess of Al2O3 (0.22 mol) led to the formation of secondary phases. SEM observation revealed the good interconnection between LLCZT grains and the distribution of the glassy phase formed by Li3BO3 and Al2O3. Effective combination of 0.21 mol of Al2O3 and 0.80 mol of Li3BO3 produced denser material with high relative density of 95% and high Li-ion conduction of 1 x 10(-4) S/cm at 32 degrees C.
  • Masanori Nagao, Akira Miura, Ikuo Ueta, Satoshi Watauchi, Isao Tanaka
    SOLID STATE COMMUNICATIONS 245 11 - 14 2016年11月 [査読有り][通常論文]
     
    Resistivities of single-crystalline as well as poly-crystalline samples of CeOBiS2 without fluorine doping were measured at temperatures down to 0.13 K, and were compared with those of poly-crystalline LaOBiS2 and PrOBiS2. Both poly-crystalline and single-crystalline CeOBiS2 exhibited zero resistivity below 1.2 K while poly-crystalline LaOBiS2 and PrOBiS2 did not show zero resistivity down to 0.13 K. Superconducting transition temperature of CeOBiS2 was reduced by increasing the applied current density. The superconductivity of CeOBiS2 without chemical doping is likely triggered by the carriers induced by the valence fluctuation between Ce3+ and Ce4+. (C) 2016 Elsevier Ltd. All rights reserved.
  • Takei,Takahiro, Iidzuka, Kiyoaki, Miura, Akira, Yanagida, Sayaka, Kumada, Nobuhiro, Magome, Eisuke, Moriyoshi, Chikako, Kuroiwa, Yoshihiro
    Langmuir 32 39 9993 - 9999 2016年10月 [査読有り][通常論文]
     
    Adsorption competencies of rare earth metal cations in gamma-zirconium phosphate were examined by ICP, synchrotron X-ray diffraction (SXRD), and ab initio simulation: The adsorption amounts are around 0.06-0.10 per zirconium phosphate. From the SXRD patterns of the adsorbed samples, the basal spacing estimated by c sin beta increased linearly with an increasing ionic radius of rare earth metal cation, though a and b lattice constants show no change. These SXRD patterns Can be classified into four groups that have different super lattices. The four superlattices have multiplicities of x131, x241, and x221 for the xabe axis, and the location of the rare earth metal cation in the original unit cell changes depending on the superlattice cell. In the x131 superlattice, Yb and Et occupied the site near the zirconium phosphate layer, though La and Ce in the x221 superlattice remained in the center position between the phosphate sheet. For the ab initio simulation of gamma-ZrP with the typical rare earth metal cations (Tb, Eu, Dy, and La), the results of simulation show a similar tendency of the position estimated by SXRD refinements.
  • Masaya Fujioka, Manabu Ishimaru, Taizo Shibuya, Yoichi Kamihara, Chihiro Tabata, Hiroshi Arnitsuka, Akira Miura, Masashi Tanaka, Yoshihiko Takano, Hideo Kaiju, Junji Nishii
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 31 9927 - 9934 2016年08月 [査読有り][通常論文]
     
    A novel superconductor, LaPt5As, which exhibits a new crystal structure was discovered by high-pressure synthesis using a Kawai-type apparatus. A superconducting transition temperature was observed at 2.6 K. Depending on the sintering pressure, LaPt5As has superconducting and non superconducting phases with different crystal structures. A sintering pressure of around 10 GPa is effective to form single-phase superconducting LaPt5As. This material has a very unique crystal structure with an extremely long c lattice parameter of over 60 A and corner-sharing tetrahedrons composed of network like Pt layers. Density functional theory calculations have suggested that the superconducting current flows through these Pt layers. Also, this unique layered structure characteristic of LaPt5As is thought to play a key role in the emergence of superconductivity. Furthermore, due to a stacking structure which makes up layers, various structural modifications for the LaPt5As family are conceivable. Since such a high-pressure synthesis using a Kawai-type apparatus is not common in the field of materials science, there is large room for further exploration of unknown phases which are induced by high pressure in various materials.
  • Miura, Akira, Rosero-Navarro, Carolina, Masubuchi, Yuji, Higuchi, Mikio, Kikkawa, Shinichi, Tadanaga, Kiyoharu
    Angewandte Chemie International Edition 55 28 7963 - 7967 2016年07月 [査読有り][通常論文]
     
    The catalytic activity of manganese oxynitrides in the oxygen reduction reaction (ORR) was investigated in alkaline solutions to clarify the effect of the incorporated nitrogen atoms on the ORR activity. These oxynitrides, with rock-salt-like structures with different nitrogen contents, were synthesized by reacting MnO, Mn2O3, or MnO2 with molten NaNH2 at 240–280 °C. The anion contents and the Mn valence states were determined by combustion analysis, powder X-ray diffraction, and X-ray absorption nearedge structure analysis. An increase in the nitrogen content of rock-salt-based manganese oxynitrides increases the valence of the manganese ions and reinforces the catalytic activity for the ORR in 1 M KOH solution. Nearly single-electron occupancy of the antibonding eg states and highly covalent Mn−N bonding thus enhance the ORR activity of nitrogen-rich manganese oxynitrides.
  • Satoshi Ishii, Yasuaki Hongu, Akira Miura, Masanori Nagao
    APPLIED PHYSICS EXPRESS 9 6 63101  2016年06月 [査読有り][通常論文]
     
    The praseodymium (Pr) valence in superconducting PrO1-xFxBiS2 (x = 0.13; 0.23) single crystals was evaluated by X-ray photoelectron spectroscopy. The Pr 3d core level is split into 3d(3/2) and 3d(5/2) levels. Both PrO1-xFxBiS2 and Pr2S3, which contain only Pr3+, showed 3d spectra at a lower binding energy than Pr6O11, which contains both Pr3+ and Pr4+. Neither PrO1-xFxBiS2 nor Pr2S3 showed the characteristic satellites of Pr4+ in 3d(5/2) spectra. The valence fluctuation between the Pr3+ and Pr4+ states was not confirmed, suggesting that Pr3+ is dominant in PrO1-xFxBiS2 (x = 0.13; 0.23) single crystals. (C) 2016 The Japan Society of Applied Physics
  • Octavianti Naa, Nobuhiro Kumada, Akira Miura, Takahiro Takei, Masaki Azuma, Yoshihiro Kusano, Kengo Oka
    INORGANIC CHEMISTRY 55 12 5747 - 5749 2016年06月 [査読有り][通常論文]
     
    A new high-pressure polymorph of NaBiO3 (hereafter beta-NaBiO3) was synthesized under the conditions of 6 GPa and 600 degrees C. The powder X-ray diffraction pattern of this new phase was indexed with a hexagonal cell of a = 9.968(1) angstrom and c = 3.2933(4) angstrom. Crystal structure refinement using synchrotron powder X-ray diffraction data led to R-WP = 8.53% and R-P = 5.55%, and the crystal structure was closely related with that of Ba2SrY6O12. No photocatalytic activity for phenol decomposition was observed under visible-light irradiation in spite of a good performance for its mother compound, NaBiO3. The optical band-gap energy of beta-NaBiO3 was narrower than that of NaBiO3, which was confirmed with density of states curves simulated by first-principles density functional theory calculation.
  • Yuta Fujii, Yusaku Suto, Akira Miura, Mikio Higuchi, Kiyoharu Tadanaga
    CHEMISTRY LETTERS 45 6 652 - 654 2016年06月 [査読有り][通常論文]
     
    An all-solid-state lithium secondary battery using a NiPS3 electrode and a 80Li(2)S center dot 20P(2)S(5) glass solid electrolyte was fabricated, and the charge-discharge cycle performance of the corresponding all-solid-state cell was investigated. This all solid-state cell exhibited a stable reversible capacity of about 80 mAh g(-1) after 30 cycles with a current density of 64 mu A cm(-2) at room temperature. This suggests that NiPS3 has a potential as an electrode active material in all-solid-state lithium secondary batteries using Li2S-P2S5 solid electrolytes.
  • Takahiro Takei, Hiroki Fuse, Akira Miura, Nobuhiro Kumada
    APPLIED CLAY SCIENCE 124 236 - 242 2016年05月 [査読有り][通常論文]
     
    Topotactic transformation of film-shaped samples comprising a layered double hydroxide (LDH) to a metal oxide phase was performed by a hydrothermal or heat treatment The degree of transformation was examined by X-ray photoelectron spectroscopy (XPS) and synchrotron X-ray diffraction (SXRD). The LDH film prepared as a raw material by a reflux process with urea was composed of plate-shaped particles that were partially perpendicular to the substrate. For the transformation, the LDH powder and film were treated hydrothermally at 90, 120, and 200 degrees C in a LiOH aqueous solution or heated to 400, 600, and 800 degrees C with a LiOH center dot H2O contact. The film shape and morphology of the LDH particles were retained after the hydrothermal treatment at 120 degrees C. XPS and SXRD confirmed that two types of LDH with different compositions, Ni:Co = 62:38 and 90:10, were formed in the as-prepared LDH. In the case of the sample treated hydrothermally, metal hydroxide with no intercalated anion within the interlayer space was observed and the metal oxyhydroxide formed with a ratio of approximately 15%. For the heated samples, the transformation to LiNi1-xCoxO2-related materials was carried out by heating to 600 or 800 degrees C. 2016 Elsevier B.V. All rights reserved.
  • Structure, Superconductivity, and Magnetism of Ce(O,F)BiS2 Single Crystals
    Akira Miura, Masanori Nagao, Takahiro Takei, Satoshi Watauchi, Yoshikazu Mizuguchi, Yoshihiko Takano, Isao Tanaka, Nobuhiro Kumada
    CRYSTAL GROWTH & DESIGN 16 4 2459  2016年04月 [査読有り][通常論文]
  • Mizuguchi, Yoshikazu, Miura, Akira, Nishida, Atsuhiro, Miura, Osuke, Tadanaga, Kiyoharu, Kumada, Nobuhiro, Lee, C. H, Magome, Eisuke, Moriyoshi, Chikako, Kuroiwa, Yoshihiro
    Journal of Applied Physics 119 15 155103  2016年04月 [査読有り][通常論文]
     
    We examined the crystal structure of the new thermoelectric material LaOBiS2-xSex, whose thermoelectric performance is enhanced by Se substitution, by using powder synchrotron X-ray diffraction and Rietveld refinement. The emergence of metallic conductivity and enhancement of the thermoelectric power factor of LaOBiS2-xSex can be explained with the higher in-plane chemical pressure caused by the increase of Se concentration at the in-plane Ch1 site (Ch = S, Se). High-temperature X-ray diffraction measurements for optimally substituted LaOBiSSe revealed anomalously large atomic displacement parameters (U-iso) for Bi and Ch atoms in the BiCh(2) conduction layers. The anisotropic analysis of the atomic displacement parameters (U-11 and U-33) for the in-plane Bi and Ch1 sites suggested that Bi atoms exhibit large atomic displacement along the c-axis direction above 300 K, which could be the origin of the low thermal conductivity in LaOBiSSe. The large Bi vibration along the c-axis direction could be related to in-plane rattling, which is a new strategy for attaining low thermal conductivity and phonon-glass-electron-crystal states. Published by AIP Publishing.
  • N. C. Rosero-Navarro, T. Yamashita, A. Miura, M. Higuchi, K. Tadanaga
    SOLID STATE IONICS 285 6 - 12 2016年02月 [査読有り][通常論文]
     
    Li7La3(Zr-2 (-) Nb-x(x))O-12 (LLZNbO, x = 0-1.5) was prepared using sol-gel process at low temperatures. Additives (LiBO2 and Li3BO3) were used to improve the sintering of the ceramic electrolyte at low temperatures. XRD patterns of the calcined powder displayed the formation of cubic garnet phase between 600 and 700 degrees C in composition with higher Nb content (LLZNbO, x >= 0.5). The density of composites with additives sintered at 900 degrees C achieves 90%. In composites sintered with LiBO2, the presence of La2Zr2O7 was detected, whereas single cubic phase was obtained for the composites sintered with Li3BO3. The ion conductivity attained was 7 x 10(-5) S/cm at 30 degrees C using 6.5 wt% Li3BO3 (900 degrees C), representing enhancement by more than two orders of magnitude compared to the material without additives. Improvements of Li ion conductivity can be interpreted by the enhanced relative density as the result of the rearrangement of particles produced by adequate concentration of the additive. (C) 2015 Elsevier B.V. All rights reserved.
  • Mirza H. K. Rubel, Takahiro Takei, Nobuhiro Kumada, M. Mozahar Ali, Akira Miura, Kiyoharu Tadanaga, Kengo Oka, Masaki Azuma, Masatomo Yashima, Kotaro Fujii, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, James R. Hester, Maxim Aydeev
    CHEMISTRY OF MATERIALS 28 2 459 - 465 2016年01月 [査読有り][通常論文]
     
    Double-perovskite Bi oxides are a new series of superconducting materials, and their crystal structure and superconducting properties are under investigation. In this paper, we describe the synthesis and characterization of a new double-perovskite material that has an increased superconductive transition temperature of 31.5 K. The structure of the material was examined using powder neutron diffraction (ND), synchrotron X-ray diffraction (SXRD), and transmission electron microscopy (TEM). Rietveld refinement of the sample based on ND and SXRD data confirmed an A-site-ordered (K-1.00)(Ba-1.00)(3)(Bi0.89Na0.11)(4)O-12 double-perovskite-type structure with the space group Im (3) over barm (No. 229). This structural analysis revealed the incorporation of Na with Bi in the structure and a bent bond between (Na, Bi)-O-(Na, Bi). TEM analyses also confirmed a cubic double-perovskite structure. This hydrothermally synthesized compound exhibited a large shielding volume fraction, exceeding 100%, with onset of superconductivity at similar to 31.5 K. Its electrical resistivity dropped near onset at similar to 28 K, and zero resistivity was confirmed below 13 K. The calculated band structure revealed that the metallicity of the compound and the flatness of the conduction bands near the Fermi level (E-F) are important for the appearance of superconductivity.
  • Akira Miura, Yoshikazu Mizuguchi, Takahiro Takei, Nobuhiro Kumada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, Kiyoharu Tadanaga
    SOLID STATE COMMUNICATIONS 227 19 - 22 2016年01月 [査読有り][通常論文]
     
    The band gaps of isostructural Bi2OS2 and LaOBiS2 were examined using optical absorption and discussed with the band structures calculated based on the crystal structures determined, using synchrotron X-ray diffraction. The Bi 6p and S 3p orbitals in the Bi-S plane were computationally predicted to constitute the bands near the Fermi level. The optical reflectance spectra of Bi2OS2 and LaOBiS2 showed optical band gaps of similar to 1.0 eV, which were close to the computationally calculated direct band gaps of similar to 0.8 eV. Our results show that Bi2OS2 and LaOBiS2 are semiconductors containing direct band gaps of 0.8-1.0 eV, and they are suggested to be candidates for optoelectronic materials in the near-infrared region without highly toxic elements. (C) 2015 Elsevier Ltd. All rights reserved.
  • Akira Miura, Yoshikazu Mizuguchi, Tsuyoshi Sugawara, Yongming Wang, Takahiro Takei, Nobuhiro Kumada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, Osuke Miura, Kiyoharu Tadanaga
    INORGANIC CHEMISTRY 54 21 10462 - 10467 2015年11月 [査読有り][通常論文]
     
    The relationship between the structure and superconductivity of Bi4O4S3 powders synthesized by heating under ambient and high pressures was investigated using synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM) observation. The Bi4O4S3 powders synthesized under ambient pressure exhibited a strong superconductivity (diamagnetic) signal and zero resistivity below similar to 4.5 K, while the Bi4O4S3 powder synthesized by the high-pressure method exhibited a low-intensity signal down to 2 K. Further annealing of the latter Bi4O4S3 powder under ambient pressure led to the development of a strong signal and zero resistivity. The crystal structures of all Bi4O4S3 phases consisted of Bi4O4Bi2S4 blocks including a Bi-S layer and anion(s) sandwiched between Bi4O4Bi2S4 blocks, but minor structural differences were detected. A comparison of the structures of the superconductive and nonsuperconductive Bi4O4S3 samples suggested that the superconductive Bi4O4S3 phases had slightly smaller lattice parameters. The average structures of the superconductive Bi4O4S3 phases were characterized by a slightly shorter and less bent BiS plane. Raman spectroscopy detected vibration of the S-O bonds, which can be attributed to sandwiched anion(s) such as SO42-. TEM observation showed stacking faults in the superconductive Bi4O4S3 phases, which indicated local fluctuation of the average structures. The observed superconductivity of Bi4O4S3 was discussed based on impurity phases, enhanced hybridization of the px and py orbitals of the Bi-S plane within Bi4O4Bi2S4 blocks, local fluctuation of the average structures, compositional deviation related to suspicious anion(s) sandwiched between Bi4O4Bi2S4 blocks, and the possibility of suppression of the charge-density-wave state by enriched carrier concentrations.
  • Yoshikazu Mizuguchi, Akira Miura, Joe Kajitani, Takafumi Hiroi, Osuke Miura, Kiyoharu Tadanaga, Nobuhiro Kumada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa
    SCIENTIFIC REPORTS 5 14968  2015年10月 [査読有り][通常論文]
     
    BiCh(2)-based compounds (Ch: S, Se) are a new series of layered superconductors, and the mechanisms for the emergence of superconductivity in these materials have not yet been elucidated. In this study, we investigate the relationship between crystal structure and superconducting properties of the BiCh(2)-based superconductor family, specifically, optimally doped Ce1-xNdxO0.5F0.5BiS2 and LaO0.5F0.5Bi(S1-ySey)(2). We use powder synchrotron X-ray diffraction to determine the crystal structures. We show that the structure parameter essential for the emergence of bulk superconductivity in both systems is the in-plane chemical pressure, rather than Bi-Ch bond lengths or in-plane Ch-Bi-Ch bond angle. Furthermore, we show that the superconducting transition temperature for all REO(0.5)F(0.5)BiCh(2) superconductors can be determined from the in-plane chemical pressure.
  • N. Kumada, A. Miura, T. Takei, S. Nishimoto, Y. Kameshima, M. Miyake, Y. Kuroiwa, C. Moriyoshi
    Journal of Asian Ceramic Societies 3 3 251 - 254 2015年09月01日 [査読有り][通常論文]
     
    Two new cadmium bismuthates, CdBi2O6 and Cd0.37Bi0.63O1.79, were prepared by hydrothermal reaction using NaBiO3·nH2O as one of the starting compounds. The crystal structures of these compounds were refined by using synchrotron X-ray powder diffraction data. The former bismuthate has a MnSb2O6-type structure with a hexagonal cell (space group: P321) the cell parameters were a=9.3641(7) and c=4.9523(3)Å, and the final R-factors were Rwp=4.59% and Rp=3.04%. The latter bismuthate has a fluorite-type structure with a cubic cell (space group: Fm3-m) of a=5.4110(4)Å, and the final R-factors were Rwp=4.79% and Rp=3.57%. These new bismuthates exhibit no photocatalytic activity under visible light.
  • Akira Miura, Kiyoharu Tadanaga, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, Takei Takahiro, Nobuhiro Kumada
    JOURNAL OF SOLID STATE CHEMISTRY 229 272 - 277 2015年09月 [査読有り][通常論文]
     
    Crystallographic and electronic structures of Nb-, Mo-, Ta-, and W-based layered oxides, oxynitrides, and nitrides were analyzed to elucidate the structural relationship between layered oxides and nitrides consisting of octahedral and trigonal-prismatic layers. The electron density, as derived by synchrotron X-ray analysis of LiNbO2 and Ta5-x(O,N)(6), showed orbital overlaps between Nb-Nb and Ta-Ta metals in the trigonal layers. Computational calculations based on DFT exhibited that these overlaps stabilized these structures by lowering the hybridization states composed of the d(xy), d(x2-y2), and d(z2) orbitals below the Fermi level. Crystal structures and formation energies suggest that tuning the Fermi level through the substitutions and vacancies of the cation/anion sites determines the structural preferences of the coordination. The properties and syntheses of these compounds are briefly described. This study enhances the understanding of layered oxides, oxynitrides, and nitrides to further the development of new synthetic approaches, compounds, and applications. (C) 2015 Elsevier Inc. All rights reserved.
  • Qiang Dong, Shu Yin, Mizuki Yoshida, Xiaoyong Wu, Bin Liu, Akira Miura, Takahiro Takei, Nobuhiro Kumada, Tsugio Sato
    MATERIALS RESEARCH BULLETIN 69 116 - 119 2015年09月 [査読有り][通常論文]
     
    Alkaline earth metal doped tin oxide (SnO2) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl4 center dot 5H(2)O and A(NO3)(2)center dot xH(2)O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO2 and A-doped SnO2 hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer-Emmet-Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO2 hollow nanospheres calcined at 1000 degrees C for 20 h with a BET surface area of 61 m(2) g(-1) exhibited the considerably high OSC of 457 mu mol-O g(-1) and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material. (C) 2014 Elsevier Ltd. All rights reserved.
  • Nagao, Masanori, Miura, Akira, Watauchi, Satoshi, Tanaka, Isao
    Japanese Journal of Applied Physics 54 8 83101  2015年08月 [査読有り][通常論文]
     
    The high anisotropy in RO1-aFaBiS2 (R denotes a rare-earth element) superconductors demonstrates their potential use as intrinsic Josephson junctions, considering the weak coupling among BiS2-PrO(F)-BiS2 (superconducting-normal-superconducting) layers along the c-axis. We grew PrO1-aFaBiS2 single crystals using CsCl/KCl flux. The superconducting anisotropies of the grown single crystals were estimated to be approximately 40-50 from the effective mass model. The c-axis transport properties were characterized using single-crystal s-shaped intrinsic Josephson junctions with a focused ion beam. Along the c-axis, the crystals showed zero resistivity at 2.7 K and a critical current density of 1.33 x 10(3) A/cm(2) at 2.0 K. The current-voltage curve along the c-axis displayed hysteresis. The c-axis transport measurements under a magnetic field parallel to the ab-plane revealed a "lock-in" state due to the Josephson vortex flow, indicating that BiS2 superconductors are promising candidates for intrinsic Josephson junctions. (C) 2015 The Japan Society of Applied Physics
  • Nan Xu, Takahiro Takei, Akira Miura, Nobuhiro Kumada
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 123 1440 690 - 694 2015年08月 [査読有り][通常論文]
     
    Ag-intercalated and Bi-intercalated layered perovskite were fabricated by ion-exchanged process. The XRD and XPS confirm the phase transformation of the Ag-ion exchanged layered perovskite from Dion-Jacobson to Ruddlesden-Popper phase by heating at higher than 200 degrees C. In the case of Bi ion-exchange perovskite, the product remained Dion-Jacobson phase during the heat treatment. For the Ag-intercalated sample, Ruddlesden-Popper type photocatalyst by heating at 500 degrees C can degrade 20 ppm phenol solution to 6ppm in 3 h under Xe light, which has superior photocatalytic activity to Dion-Jacobson phase Ag0.67H0.33LaNb2O7. For the Bi-intercalated sample, Dion-Jacobson type photocatalyst can degrade phenol from 20 to 12 ppm in 3 h. From first principle DFT simulation, high photocatalytic activity may be due to the new Ag 4d, O 2p and Nb 4d hybridized band at the highest of the valence band for Ag-included, and to the new Bi 6p band at the lowest of the conduction band for Bi-included samples. (C) 2015 The Ceramic Society of Japan. All rights reserved.
  • Nan Xu, Takahiro Takei, Akira Miura, Nobuhiro Kumada, Ken-ichi Katsumata, Nobuhiro Matsushita, Kiyoshi Okada
    LANGMUIR 31 27 7660 - 7665 2015年07月 [査読有り][通常論文]
     
    A novel photocatalyst consisting of an intercalated perovskite H1-2xPtxLaNb2O7 was fabricated by ion, exchange. Synchrotron X-ray diffraction and X-ray photoelectron spectroscopy results confirmed that Pt2+ exists within the interlayer space of the layered perovskite: H1-2xPtxLaNb2O7 composed of layered niobate perovskite. and intercalated Pt2+ completely degraded a 20 ppm phenol solution in 3 h under irradiation by Xe light, which exhibits photocatalytic activity superior to those of RbLaNb2O7, Pt-deposited RbLaNb2O7, and HLaNb2O7. From first-principles density functional theory simulation, high photocatalytic activity Of H1-2xPtxLaNb2O7 is attributed to the emergence of a new O 2p-Pt 5d hybridized band on top of the valence band.
  • Mirza H. K. Rubel, Takahiro Takei, Nobuhiro Kumada, M. M. Ali, Akira Miura, Kiyoharu Tadanaga, K. Oka, M. Azuma, E. Magomae, C. Moriyoshi, Y. Kuroiwa
    JOURNAL OF ALLOYS AND COMPOUNDS 634 15 208 - 214 2015年06月 [査読有り][通常論文]
     
    A new type of bismuth-oxide-based superconductor was prepared by a hydrothermal reaction at 240 degrees C. The synchrotron X-ray powder diffraction pattern reveals a simple perovskite-type structure with a cubic cell of a = 4.28877(1) angstrom with space group Pm-(3) over barm. The chemical composition of this cubic perovskite oxide was formulated as (Ba0.82K0.18)(Bi0.53Pb0.47)O-3 after structural refinement using synchrotron X-ray powder diffraction and chemical analysis data. The cubic microstructure and compositional homogeneity were confirmed by scanning electron microscopy analysis. This compound exhibited a diamagnetic signal with a shielding volume fraction of similar to 64% with an onset of approximately 22.8 K. Its resistivity started to drop at similar to 15 K, and zero resistivity was observed below 4 K. The thermal decomposition of this simple perovskite structure started above 600 degrees C. Finally, the calculated band structure also exhibited metallic behavior at ambient conditions. (C) 2015 Elsevier B.V. All rights reserved.
  • Yoneyama, Naoki, Kurobe, Takahide, Iguchi, Satoshi, Miura, Akira, Takei, Takahiro, Kumada, Nobuhiro, Sasaki, Takahiko
    Journal of the Physical Society of Japan 84 3 84 - 3 2015年03月 [査読有り][通常論文]
     
    We have studied the structural, magnetic, and dielectric properties of the dimer-Mott insulator beta'-(BEDT-TTF)(2)(ICl2)(1-x)(AuCl2)(x). The AuCl2 substitution for ICl2 decreases the lattice length in the interlayer direction, leading to uniaxial chemical pressure with a negligible effect on the intralayer donor stacking. The variation of the Neel temperature as a function of x is explained on the basis of chemical pressure accompanied by anion disorder, while the dielectric response does not indicate the effect of chemical pressure. This suggests that the charge degrees of freedom are attributed to the intralayer origin such as the charge fluctuation of donor molecules induced by an electric field.
  • Masanori Nagao, Akira Miura, Satoshi Watauchi, Takahiro Takei, Nobuhiro Kumada, Isao Tanaka
    JOURNAL OF CRYSTAL GROWTH 412 15 16 - 19 2015年02月 [査読有り][通常論文]
     
    Single crystals of Cu(In,Ga)S-2 were successfully grown using CsCl flux in vacuum The grown single crystals were typically 3-4 mm with unshaped form. The Cu(In,Ga)S-2 single crystals with various Ga concentration were obtained by control of the Ga concentration in the starting materials. The optical band-gaps of obtained single crystals were estimated from the reflectance spectrum The optical band-gap changed between 142 and 240 eV at room temperature with dependence on the Ga concentration. (C) 2014 Elsevier B.V. All rights reserved.
  • Kiyoharu Tadanaga, Kohei Igarashi, Takashi Kubota, Akira Miura, Mikio Higuchi
    ECS Transactions 69 17 385 - 389 2015年 [査読有り][通常論文]
     
    Layered double hydroxides (LDHs) intercalated with CO3 2- show high hydroxide ion conductivity of the order of 10-3 S cm-1 under 80% relative humidity. In the present study, (Ni, Mn)-Al LDHs and (Ni, Mn)-Fe LDHs intercalated with CO32- were prepared. The conductivity of (Ni, Mn)-Al LDH and (Ni, Mn)-Fe LDH was higher than that of Ni-Al LDH or Ni-Fe LDH. These LDHs were applied to the catalyst layer in an alkaline fuel cell for the improvement of the oxygen reduction reaction (ORR) at the triple phase boundary (TPB) in the catalyst layer. The addition of LDHs to the catalyst layer increased the current for ORR, indicating that hydroxide ion conducting LDHs introduced OH- conducting paths and increased TPB region within the catalyst layer. Above all, the addition of (Ni, Mn)-Fe LDH to the catalyst layer more effectively increased the reduction current for ORR than the addition of (Ni, Mn)-Al LDHs or Ni-Fe LDH. H2-O2 fuel cells with Ni-Al or Mg-Al LDHs as an electrolyte and MnO2 as the cathode catalyst were fabricated. The H2-O2 fuel cells were confirmed to be operated.
  • Akira Miura, Masanori Nagao, Takahiro Takei, Satoshi Watauchi, Yoshikazu Mizuguchi, Yoshihiko Takano, Isao Tanaka, Nobuhiro Kumada
    CRYSTAL GROWTH & DESIGN 15 1 39 - 44 2015年01月 [査読有り][通常論文]
     
    The crystal structures of Ce(O,F)BiS2 synthesized from starting materials with five different F contents were determined by single-crystal X-ray analysis. An increase in F content in the starting materials slightly increased F incorporation in the grown single crystals. The grown crystals with various F contents showed similar layered structures, but minor structural changes were observed with different conductive and magnetic properties. Crystals grown from higher F content were found to have a nearly flat Bi-S plane and elongated Ce-(O,F) bond, and showed superconductive transition below similar to 3 K and spontaneous magnetization below similar to 7 K. The calculated density of states based on this structural analysis predicted that hybridized Bi 6p-S 3p orbitals intersect the Fermi level and that Ce states are located near the Fermi level. The effect of structural change on superconductivity and long-range magnetic ordering has been discussed.
  • Akira Miura, Takahiro Takei, Nobuhiro Kumada
    Journal of Asian Ceramic Societies 2 4 326 - 328 2014年12月01日 [査読有り][通常論文]
     
    We report on the low-temperature synthesis of submicron-sized Cu3N powder produced from CuO and NaNH2 powder mixture by heating at 150-190°C in a Teflon-sealed autoclave. The structure was the anti-RuO3 type with a lattice parameter of 0.3814(1) nm, and strong optical absorption was observed below ~1.9eV. This synthesis method has the potential of facile control of the reaction with less use of ammonia sources.
  • Takahiro Takei, Nanae Muraki, Nan Xu, Akira Miura, Nobuhiro Kumada
    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 459 186 - 193 2014年10月 [査読有り][通常論文]
     
    A layered perovskite was fluorinated by polytetrafluoroethylene (PTFE) and then exfoliated to prepare a solution of fluorinated-perovskite nanosheets. Dion-Jacobson-type layered perovskites, RbLaNb2O7 and KCa2Nb3O10, were prepared in solid-state reactions at 950 and 1100 degrees C, respectively. The perovskites were fluorinated using PTFE at 400 degrees C, upon which their color changed from white to gray or black and their electrical conductivity increased to the order of 10(-4)-10(-5) S/m. The tetrabutyl ammonium cations(TBA(+)) in each fluorinated layered perovskite were first intercalated by tetrabutylammonium hydroxide(TBAOH) in H2O and then exfoliated in an acetonitrile solution for electrodeposition. Aniline was added to the solution as a monomer and electrodeposition was carried out in the acetonitrile solution for formation of a hybrid film. X-ray diffraction patterns confirmed that the polyaniline molecules could be intercalated within the interlayer space. Despite the fluorination, the volumetric filling fractions of polyaniline in the interlayer space were around 0.4 and 0.2 for the respective samples from RbLaNb2O7 and KCa2Nb3O10. The electrochemical specific capacitances of the deposited hybrid films increased steeply from below 50 F/g to above 230-250 F/g owing to the fluorination. (C) 2014 Elsevier B.V. All rights reserved.
  • Xu, Nan, Takei, Takahiro, Miura, Akira, Kumada, Nobuhiro
    Journal of Ion Exchange 25 242 - 247 2014年08月 [査読有り][通常論文]
  • Nobuhiro Kumada, Nan Xu, Akira Miura, Takahiro Takei
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 1426 509 - 512 2014年06月 [査読有り][通常論文]
     
    Two new pentavalent bismuthates, CaBi2O6-x center dot 1.1H(2)O and PbBi2O6-x center dot H2O were prepared from NaBiO3 center dot nH(2)O. Broadened X-ray powder diffraction patterns for both bismuthates were indexed to the hexagonal cell observed for PbSb2O6-type SrBi2O6. The lattice parameters were a = 0.555(1) and c = 0.530(1) nm for CaBi2O6-x center dot 1.1H(2)O and a = 0.5544(4) and c = 0.531(1) nm for PbBi2O6-x center dot H2O. At elevated temperatures, the Ca derivative decomposed to Ca3Bi8O15 and an unknown phase via the fluorite-type structure, whereas the Pb derivative changed to Pb1/3Bi2/3O4/3 via the fluorite-type (Pb1/3Bi2/3)O-1.4. Both Ca and Pb derivatives exhibited photocatalytic activity for the decomposition of phenol under visible light irradiation, although the adsorption of phenol was observed under dark conditions. The fluorite-type phases evolved from the Ca and Pb derivatives did not adsorb phenol under dark conditions, and their photocatalytic activities toward phenol decomposition under visible light were inferior to those of the parent compounds. (C) 2014 The Ceramic Society of Japan. All rights reserved.
  • Rubel, Mirza HK, Miura, Akira, Takei, Takahiro, Kumada, Nobuhiro, Mozahar Ali, M, Nagao, Masanori, Watauchi, Satoshi, Tanaka, Isao, Oka, Kengo, Azuma, Masaki
    Angewandte Chemie 53 14 3599 - 3603 2014年04月 [査読有り][通常論文]
     
    国際共同研究
  • Nobuhiro Kumada, Mirza Humaun Kabir Rubel, Akira Miura, Takahiro Takei
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 1424 307 - 309 2014年04月 [査読有り][通常論文]
     
    Spinel-type LiTi2O4 was prepared directly by the reaction of lepidocrocite-type potassium titanate and molten LiCl at 750-850 degrees C in a stream of H-2 gas. The Li/Ti ratio in the spinel-type phase prepared at 850 degrees C was 0.54, and the lattice parameter and superconductive critical temperature T-c were alpha = 8.3935(2) angstrom and 12.3 K, respectively. The product at 750 degrees C exhibited no superconductive diamagnetism down to 2.5 K, and the product at 800 C showed weak superconductive diamagnetism at 10.5 K. The morphology of the particles prepared at 850 degrees C showed an irregular shape with a particle size of 1-10 mu m. (C) 2014 The Ceramic Society of Japan. All rights reserved.
  • Akira Miura, Masanori Nagao, Takahiro Takei, Satoshi Watauchi, Isao Tanaka, Nobuhiro Kumada
    JOURNAL OF SOLID STATE CHEMISTRY 212 213 - 217 2014年04月 [査読有り][通常論文]
     
    The crystal structures of superconducting LaO1-xFxBiS2 (x similar to 0.23, 0.46) were determined by single-crystal X-ray diffraction analysis. Their space group was P4/nmm. Distortion of the Bi-S plane changed when the F content was increased from 0.23 to 0.46, and a nearly flat Bi-S plane was formed at x-0.46. Computational calculations supported this effect of F doping on distortion of Bi-S plane. LaO1-xFxBiS2 with higher F contents were computationally predicted to be thermodynamically more unstable under ambient pressure. We discussed the bonding, conductivities, and synthetic routes of LaO1-xFxBiS2. (C) 2014 Elsevier Inc. All rights reserved.
  • Akira Miura, Takahiro Takei, Nobuhiro Kumada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa
    JOURNAL OF ALLOYS AND COMPOUNDS 593 154 - 157 2014年04月 [査読有り][通常論文]
     
    The crystal structures of FexWN2 (x similar to 0.74, 0.90) and their magnetic properties were investigated. The structural studies reveal the formation of ion defects with different concentrations in the two-dimensional iron triangular lattice by analyzing the synchrotron radiation X-ray diffraction data. The magnetic measurements demonstrate that the Fe0.74WN2 phase shows ferromagnetism at 300 K, while the less defective Fe0.90WN2 phase exhibits no ferromagnetism. A decrease of temperature to 5 K significantly suppresses the room-temperature ferromagnetism of the Fe0.74WN2 phase. We attribute the emergence of ferromagnetism in FexWN2 to the increases of defect concentration and thermal displacement in the iron triangular lattice. (C) 2014 Elsevier B.V. All rights reserved.
  • Dong, Qiang, Yin, Shu, Guo, Chongshen, Wu, Xiaoyong, Kumada, Nobuhiro, Takei, Takahiro, Miura, Akira, Yonesaki, Yoshinori, Sato, Tsugio
    Applied Catalysis B: Environmental 147 741 - 747 2014年04月 [査読有り][通常論文]
     
    Nickel hydroxide (beta-Ni(OH)(2)) nanosheets with a diameter of 400 nm and a thickness of 20 nm were successfully synthesized by a template and surfactant-free solvothermal route in a very simple system composed of LiOH center dot H2O and Ni-naphthenate. Furthermore, porous nickel oxide (NiO) nanosheets were obtained by thermal decomposition of beta-Ni(OH)(2) nanosheets in air at 350-550 degrees C for 2 h. HRTEM and SAED results revealed that the microporous NiO nanosheets obtained at 350 degrees C were single-crystalline, and nitrogen adsorption-desorption measurements of the BET surface area and pore size of porous NiO nanosheets were 156 m(2) g(-1) and 1.7 nm, respectively. Moreover, mesoporous NiO nanosheets and macroporous NiO nanosheets could be selectively obtained by controlling thermal decomposition temperature. The formation mechanism of porous NiO nanosheets was discussed. The magnetic property and photocatalytic activity of the porous NiO nanosheets were also investigated. The porous NiO nanosheets showed enhanced photocatalytic activity for NO destruction. (C) 2013 Elsevier B.V. All rights reserved.
  • A. Miura, T. Takei, N. Kumada
    J. Ceram. Soc. Jpn. 122 1 86 - 88 2014年01月01日 [査読有り][通常論文]
  • Masanori Nagao, Akira Miura, Satoshi Demura, Keita Deguchi, Satoshi Watauchi, Takahiro Takei, Yoshihiko Takano, Nobuhiro Kumada, Isao Tanaka
    SOLID STATE COMMUNICATIONS 178 3 33 - 36 2014年01月 [査読有り][通常論文]
     
    F-substituted ROBiS2 (R=La, Ce, Nd) superconducting single crystals with different F concentrations were grown successfully using a CsCl/KCl flux. All crystals produced had a plate-like shape, with a well-developed ab-plane 1-2 mm in size. Electron probe microanalysis did not detect any Cs, K, or Cl flux components in the crystals. As-grown single crystals of F-substituted LaOBiS2 and CeOBiS2 exhibited superconductivity at about 3 K, whereas F-substituted NdOBiS2 was superconductive at approximately 5 K. The superconducting anisotropy of single crystal F-substituted LaOBiS2 and NdOBiS2 was estimated to be 30-45 according to the effective mass model, whereas the anisotropy for F-substituted CeOBiS2 single crystals was 13-21. The F-substituted CeOBiS2 single crystals exhibited a magnetic order around 7 K that apparently coexisted with superconductivity below approximately 3 K. (C) 2013 Elsevier Ltd. All rights reserved.
  • Akira Miura, Takahiro Takei, Nobuhiro Kumada
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 1421 86 - 88 2014年01月 [査読有り][通常論文]
     
    We examined the effect of polymer polytetrafluoroethylene ( PTFE) additive on the growth of InN crystals by the nitridation of LiInO2 in NaNH2 flux at 240 degrees C. LiInO2 and NaNH2 powder were heated with/without PTFE pieces in a steel crucible located inside the PTFE-lined autoclave. The additive of PTFE pieces enhanced the decomposition of LiInO2 with the mass loss of these pieces and progressed the formation of InN and In(OH)(3) byproducts. SEM and TEM images of the products using PTFE additives showed the hexagonal InN crystals of similar to 1 mu m in size, and the optical bandgap of synthesized InN was estimated as similar to 2.03 eV. We presume that fluorine in PTFE additive subtracts Li from LiInO2 and enhances the growth of InN crystals. (C)2014 The Ceramic Society of Japan. All rights reserved.
  • Nobuhiro Kumada, Akira Miura, Takahiro Takei, Masatomo Yashima
    Journal of Asian Ceramic Societies 2 2 150 - 153 2014年 [査読有り][通常論文]
     
    The crystal structures of a pentavalent bismuthate, SrBi2O6 with the PbSb2O6-type structure and a lead bismuth oxide, (Pb1/3Bi2/3)O1.4 with the fluorite-type structure were refined by using neutron diffraction data. The final R-factors were Rwp=4.49, Rp=3.46, RI=4.50 and RF=1.70% for SrBi2O6 and Rwp=5.04, Rp=3.93, RI=5.47 and RF=4.26% for (Pb1/3Bi2/3)O1.4. SrBi2O6 prepared from NaBiO3·1.4H2O is the first example of the bismuthate with the PbSb2O6-type structure. The fluorite-type lead bismuth oxide, (Pb1/3Bi2/3)O1.4 was obtained by heating the PbSb2O6-type lead bismuthate, PbBi2O5.9·H2O which was prepared also from NaBiO3·1.4H2O. © 2014 The Ceramic Society of Japan and the Korean Ceramic Society.
  • Takahiro Takei, Akira Miura, Nobuhiro Kumada
    Journal of Asian Ceramic Societies 2 3 289 - 296 2014年 [査読有り][通常論文]
     
    Co-Al and Ni-Al layered double hydroxides (LDHs) intercalated with three types of anionic molecules, dodecylsulfate (C12H25SO4-, DS), di-2-ethylsulfosuccinate ([COOC2H3EtBu]2C2H3SO3-, D2ES), and polytungstate (H2W12O4210-, HWO) were prepared by means of ion-exchange and co-precipitation processes. With the use of DS and D2ES as intercalation agents, high crystallinity was maintained after intercalation into the LDHs. In the case of HWO, the intercalated LDHs could be obtained by ion-exchange as well as co-precipitation with a decline in the crystallinity however, unreacted LDH was detected in the ion-exchange samples, and some unwanted phases such as hydroxide and pyrochlore were generated by the co-precipitation process. The maximum specific surface area and pore volume of the Ni-Al sample with intercalated HWO, prepared by the ion-exchange process were 74m2/g and 0.174mL/g, respectively. The occupancies of DS, D2ES, and HWO within the interlayer space were approximately 0.3-0.4, 0.5-0.6, and 0.1-0.2, respectively, in the Co-Al and Ni-Al LDHs. Analysis of the catalytic activity demonstrated that the DS-intercalated Ni-Al LDH sample exhibited relatively good catalytic activity for conversion of cyclohexanol to cyclohexanone. © 2014 The Ceramic Society of Japan and the Korean Ceramic Society.
  • Masanori Nagao, Satoshi Demura, Keita Deguchi, Akira Miura, Satoshi Watauchi, Takahiro Takei, Yoshihiko Takano, Nobuhiro Kumada, Isao Tanaka
    Journal of the Physical Society of Japan 82 11 113701 - 113701 2013年11月 [査読有り][通常論文]
     
    F-substituted NdOBiS2superconducting single crystals were grown using CsCl/KCl.ux. This is the.rst example of the single-crystal growth of a BiS2-based superconductor. The obtained single crystals had a plate-like shape with a size of 1-2mm and a well-developed ab-plane. The crystal structure of the grown crystals was determined by singlecrystal X-ray di.raction analysis to be the tetragonal space group P4=nmm (29) with a = 3:996(3) and c = 13:464(6)Å. The chemical formula of the grown crystals was approximately Nd0.98±0.06O 0.7±0.1F0.3±0.1Bi 0.98±0.04S2, and Cs, K, and Cl were not detected in the grown crystals by electron probe microanalysis. The grown crystals had a critical temperature of approximately 5K. The superconducting anisotropy of the single crystals was estimated to be about 30 from the e.ective mass model and the upper critical.eld. © 2013 The Physical Society of Japan.
  • Akira Miura, Takahiro Takei, Nobuhiro Kumada
    INORGANIC CHEMISTRY 52 20 11787 - 11791 2013年10月 [査読有り][通常論文]
     
    Manganese and iron nitrides are important functional materials, but their synthesis processes from oxides often require high temperatures. Herein, we show a novel meta-synthesis method for manganese and iron nitrides by low-temperature nitridation of their oxides using NaNH2 molten salt as the nitrogen source in an autoclave at 240 degrees C. With this method, nitridation of micrometer-sized oxide particles kept their initial morphologies, but the size of the primary particles decreased. The thermodynamic driving force is considered to be the conversion of oxides to sodium hydroxide, and the kinetic of nitridation is improved by the decrease of particle size and the low melting point of NaNH2. This technique as developed here has the advantages of low reaction temperature, reduced consumption of ammonia, employing nonspecialized equipment, and providing facile control of the reactions for producing nitrides from oxides.
  • Kobayashi, Miyabi, Kumada, Nobuhiro, Miura, Akira, Takei, Takahiro, Fujii, Ichiro, Wada, Satoshi
    Transactions of the Materials Research Society of Japan 38 1 53 - 55 2013年10月 [査読有り][通常論文]
  • Akira Miura, Takahiro Takei, Nobuhiro Kumada, Satoshi Wada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa
    Inorganic Chemistry 52 17 9699 - 9701 2013年09月02日 [査読有り][通常論文]
     
    Carbon, nitrogen, and oxygen are essential components in solid-state materials. However, understanding their preference on the bonding to metals has not been straightforward. Here, niobium carbide, nitride, and oxide with simple rock-salt-based structures were analyzed by first-principles calculations and synchrotron X-ray diffraction. We found that an increase in the atomic number from carbon to oxygen formed fewer and shorter bonds to metals with better hybridization of atomic orbitals. This can provide a simple guiding principle for understanding the bonding and designing carbides, nitrides, oxides, and mixed-anion compounds. © 2013 American Chemical Society.
  • Takahiro Takei, Akira Miura, Nobuhiro Kumada, Kiyoshi Okada
    Journal of Porous Materials 20 4 777 - 783 2013年08月 [査読有り][通常論文]
     
    Layered double hydroxides (LDH) containing Co or Ni as the divalent cation and Al or Fe as the trivalent cation were prepared by hydrothermal treatment. The LDH phase containing Al can be prepared at a pH of ca. 7, whereas the LDH phase containing Fe can be prepared at pH 10. The chemical composition of the LDH was estimated by the calculation of the weighted mean electronegativity of the cations present in the aqueous metal solution. The decarbonated LDHs are intercalated by sodium dodecyl sulfate and can be exfoliated in 1-butanol solution by ultrasonication. The resulting LDH aggregates with a card-house structure that can then be deposited from these exfoliated colloidal solutions by sodium carbonate. For Ni/Al and Ni/Fe LDHs, in particular, the specific surface area and pore volume drastically increased owing to the card-house texture formed by exfoliation and redeposition. © 2012 Springer Science+Business Media New York.
  • Takahiro Takei, Naoto Imazawa, Akira Miura, Nobuhiro Kumada, Kiyohiko Ogihara
    Powder Technology 237 400 - 405 2013年03月 [査読有り][通常論文]
     
    Calcium sulfite waste was successfully transformed to hydroxyapatite (HAp) by oxidation using H2O2, followed by reaction with (NH4)2HPO4 under an NH4OH atmosphere. A single phase hydroxyapatite was obtained by stirring at 60, 80, or 100°C rather than by hydrothermal treatment at 150°C. Such formation implied that the homogeneity of the solution was very important. The primary HAp particles obtained had columnar shape, which formed spongy secondary particles with a diameter of around 1μm. Such porous particles resulted from the dissolution rate of calcium sulfite. The HAp obtained had a relatively Ca-rich composition of around Ca/P=1.71, and the specific surface area was around 69m2/g. In adsorption tests for Cs+ and Cd2+ cations in artificial seawater, the prepared HAp, like the general HAp powder, could remove Cd2+ cations from the seawater. © 2012 Elsevier B.V.
  • A. Miura, T. Takei, N. Kumada
    J. Solid State Chem. 197 471 - 474 2013年01月 [査読有り][通常論文]
     
    A new layered niobate, Mg 0.5NbO 2, was synthesized from LiNbO 2 through a cation-exchange reaction with Mg 2 at 450-550 °C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO 2] - layers. It is proposed to be isostructural with LiNbO 2 (space group P6 3/mmc) with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. The lattice parameters and formation energy of Mg 0.5NbO 2 crystallized in LiNbO 2 form and other layered CaNb 2O 4 one were calculated by density functional theory. © 2012 Elsevier Inc. All rights reserved.
  • Takahiro Takei, Maho Nakamura, Akira Miura, Nobuhiro Kumada, Kiyohiko Ogihara
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 121 1409 31 - 35 2013年01月 [査読有り][通常論文]
     
    One of the calcium aluminate, 12CaO center dot 7Al(2)O(3), was synthesized from calcium sulfite hemihydrate waste which was produced as a by-product of calcium polysulfide. The calcium sulfite waste was at first pre-treated by sodium salts, Na2CO3 and Na2C2O4. Then, the waste was converted to the CaCO3 and CaC2O4, respectively. From these pre-treated sample, 12CaO center dot 7Al(2)O(3) phase was formed at 850 degrees C for the converted CaCO3 from Na2CO3 and at 650 degrees C for the converted CaC2O4 from Na2C2O4. These crystallization temperatures are much lower than from reagent CaCO3 and CaC2O4 at 1250 and 850 degrees C, respectively. The reason of such reduction of crystallized temperature may result from impurity Fe2O3 including in the by-product. Actually, addition of Fe2O3 into the reagent CaCO3 posed decrease of crystallization temperature of 12CaO center dot 7Al(2)O(3) from 1250 to 1050 degrees C. (C)2013 The Ceramic Society of Japan. All rights reserved.
  • Nobuhiro Kumada, Akira Miura, Takahiro Takei, Indri Badria Adilina, Syogo Shimazu
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 121 1409 74 - 79 2013年01月 [査読有り][通常論文]
     
    Alkaline earth metal titanates ATiO(3) (A: Mg, Ca, Sr, Ba) were prepared from two types of layered potassium titanates [K2Ti2O5 and K0.6Ti1.85O4 (hereafter, Lss)] by using alkaline earth metal molten salts [ACl(2) + A(NO3)(2) (1:1)]. For A = Ca a single phase of perovskite-type compound was prepared at 600 degrees C by using both starting compounds and the reaction temperature was lower than in 400 degrees C that of the solid state reaction with TiO2 (anatase) and CaCO3. A single phase of perovskite-type SrTiO3 was obtained at 600 and 700 degrees C for K2Ti2O5 and Lss, respectively and these temperatures were much lower than that (1200 degrees C) of the solid state reaction with TiO2 (anatase) and SrCO3. In the case of perovskite-type BaTiO3 a single phase of perovskite-type compound was prepared at 700 degrees C by using both starting compounds and also this temperature was much lower than that (above 1300 degrees C) of the solid state reaction with TiO2 (anatase) and BaCO3. Although neither K2Ti2O5 nor Lss could produce a single phase of ilmenite-type MgTiO3, it was prepared by the solid state reaction with TiO2 (anatase) and magnesium basic carbonate at 900 degrees C. A single phase of ilmenite-type CdTiO3 was prepared from K2Ti2O5 by using cadmium molten salts [CdCl2 + Cd(NO3)(2) (1:1)] at 500 degrees C. By taking account of the fact that ilmenite-type CdTiO3 transforms to perovskite-type structure, this preparative method using layered potassium titanates with molten salts preferred to crystallize perovskite-type titanates at lower temperature rather than ilmenite-type ones. (C)2013 The Ceramic Society of Japan. All rights reserved.
  • T. Takei, R. Oda, A. Miura, N. Kumada, N. Kinomura, R. Ohki, H. Koshiyama
    COMPOSITES PART B-ENGINEERING 44 1 260 - 265 2013年01月 [査読有り][通常論文]
     
    The effect of dispersion of sepiolite in a sepiolite-NBR composite on the tensile strength of the composite was examined. Fibrous sepiolite was ultrasonically treated in distilled water with various types of dispersant. The ultrasonicated sepiolite was mixed with NBR latex to form a sepiolite-NBR complex. The tensile strength of the complex was examined to evaluate the degree of dispersion of sepiolite. The tensile strength results for the composites confirmed that a lower ultrasonication frequency produced a high strength in the composite. The tensile strength actually increased from 3 to 8 MPa as a result of ultrasonication at 28 kHz. To improve and stabilize the dispersion state, five kinds of dispersant were used. The addition of two dispersants in particular, ammonium polycarboxylate and amino alcohol polyphosphate, resulted in an increase of the strength from 8 to 15-16 MPa. When the composites were heated at 450 degrees C, the strengths of the composites produced with and without the dispersant were approximately 1.4-1.7 and 0.85 MPa, respectively. Thus, the dispersant still affected the strength of the heated samples. (C) 2012 Elsevier Ltd. All rights reserved.
  • Nobuhiro Kumada, Naoko Ito, Akira Miura, Takahiro Takei, Satoshi Wada, Takayuki Watanabe
    Journal of the Ceramic Society of Japan 121 1415 544 - 549 2013年 [査読有り][通常論文]
     
    Three solid solutions [(1-x)LNN-xBaTiO3 (BT), xBaZrO3 (BZ) and xK0.5Ba0.5Ti0.5Nb0.5O 3(KBTN)] based on (Li0.12Na0.88)NbO 3(LNN) with the rhombohedral symmetry were prepared by conventional solid state reaction and their dielectric property was investigated. In the LNN-BT system in x ≤ 0.6 a secondary phase was observed as well as the perovskite-type phase and the psudo-cubic and tetragonal single phases were observed in 0.7 ≤ x ≤ 0.94 and 0.95≤ x ̄ 1.0, respectively. In LNN-BZ and LNN-KBTN systems single phases of the compounds with the rhombohedral symmetry were formed in x ≤ 0.05. The length of the a-axis increased with content of BZ or KBTN and that of the c-axis was almost unchanged except x = 0.1 for LNN-BZ. The secondary phase with the tetragonal tungsten bronze-type (TTB) structure was observed in wide composition range of these solid solutions, and LixBa2NaNb5-xMxO15(M: Ti, Zr) with the TTB-type structure was prepared and their crystal structure and dielectric property were investigated. ©2013 The Ceramic Society of Japan. All rights reserved.
  • Akira Miura, Takahiro Takei, Nobuhiro Kumada
    CRYSTAL GROWTH & DESIGN 12 9 4545 - 4547 2012年09月 [査読有り][通常論文]
     
    Nitridation of oxides above 500 degrees C is a conventional route for the synthesis of various oxynitrides and nitrides. However, this technique has the disadvantages of requiring a high temperature to break the strong metal and oxygen bonds and of low utilization efficiency of nitrogen sources such as toxic ammonia. Here, we show a simple low-temperature synthesis of InN nanocrystals via the nitridation of LiInO2 by NaNH2 flux at 240 degrees C in a Teflon-lined autoclave. The NaNH2 flux converted irregular-shaped LiInO2 powder to 50-300 nm InN nanocrystals with well-developed facets. The product crystallized in the hexagonal wurtzite structure with lattice parameters of a = 3.545 angstrom and c = 5.717 angstrom. Lithium in the starting oxide was found to be essential for this low-temperature nitridation.
  • Akira Miura, Koji Nakazawa, Takahiro Takei, Nobuhiro Kumada, Nobukazu Kinomura, Ryosaku Ohki, Hiroki Koshiyama
    CERAMICS INTERNATIONAL 38 6 4677 - 4684 2012年08月 [査読有り][通常論文]
     
    The stability of Chinese sepiolite with respect to acid, base, and heat treatments was examined based on changes that occur in its crystal structure, its morphology, its surface area, and the ions that leach into solution. Treatment in HCl for 3 h caused predominantly Mg2+ to leach and increased the surface area of the sepiolite. Increased temperature accelerated the leaching, resulting in the disappearance of the sepiolite phase above 100 degrees C. Treatment in NaOH caused Si4+ to be leached and this was accompanied by a minor change in the crystal structure of the sepiolite. Thermal treatment in air caused the manifestation of several types of dehydration behavior and the sepiolite was decomposed completely at above similar to 800 degrees C. Composite sheets of sepiolite and nitrile butadiene rubber were made from sepiolite after it had undergone various treatments. The tensile stress of each composite was measured and this is discussed with respect to its degradation features. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
  • Takahiro Takei, Hiroaki Ota, Qiang Dong, Akira Miura, Yoshinori Yonesaki, Nobuhiro Kumada, Hiroyuki Takahashi
    CERAMICS INTERNATIONAL 38 3 2153 - 2157 2012年04月 [査読有り][通常論文]
     
    Porous materials were prepared from colored waste glass by hydrothermal treatment with Na2CO3 aqueous solution. The resultant specific surface area was approximately 140 m(2)/g at maximum. Specific surface area increased at first, reached a maximum, and decreased gradually to be constant at approximately 60 m(2)/g depending on the period of hydrothermal treatment, irrespective of the concentration of Na2CO3 aqueous solution. However, the period at which the specific surface area reached maximum shortened with an increase in Na2CO3 concentration. On the other hand, the mass of the sample decreased and eventually saturated at approximately 30 mass% of the initial weight during the hydrothermal treatment. Both the dissolution of the mother glass and the formation of crystalline deposits, which were identified as calcite, zeolite-P and analcime, affected the porous structure of the treated samples. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
  • Takahiro Takei, Akira Miura, Nobuhiro Kumada
    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 396 341 - 345 2012年02月 [査読有り][通常論文]
     
    Partially substituted birnessite with Fe, Co, Ni and Cu for Mn was exfoliated to form nanosheet colloid and then their electrochemical properties were examined. The partially substituted birnessite can be exfoliated by tetrabutylammonium hydroxide acetonitrile solution. The electrodeposited films was grown from the exfoliated acetonitrile solution. The electrochemical capacitance of the films once increased at low substitution ratio and decreased with increase of the ratio. Within 10 atom% of the substitution ratio, the electrochemical capacitances are larger than that of non-substituted sample. Such increase seems to be related with DOS calculated by DV-X alpha. From calculated DOS curves, the band of 3d orbital of Mn4+ tends to broaden at low substitution ratio and be restored with further increase of the substituent. The broadening results from increase of another Mn4+ circumstance, Mn4+O6 octahedron surrounded by both Mn3+ and substituent cation. (C) 2012 Elsevier B.V. All rights reserved.
  • Yoshinori Yonesaki, Qiang Dong, Nur Suhaiza Binti Mohamad, Akira Miura, Takahiro Takei, Junji Yamanaka, Nobuhiro Kumada, Nobukazu Kinomura
    JOURNAL OF ALLOYS AND COMPOUNDS 509 35 8738 - 8741 2011年09月 [査読有り][通常論文]
     
    A simple solid-state reaction was used to apply a vitreous-phase coating onto Eu2+-doped BaCa2MgSi2O8 blue-phosphor particles. The vitreous phase was generated by liquid phase sintering at 1200 degrees C. The coated phosphor exhibited resistant to an acid dispersant. When a small amount of Al and La was added in raw materials, they were incorporated in the vitreous coating phase. (C) 2011 Elsevier B.V. All rights reserved.
  • Akira Miura, Michael Wessel, Richard Dronskowski
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 119 1392 663 - 666 2011年08月 [査読有り][通常論文]
     
    The electronic structure (band structure, DOS and COHP) of the delafossite nitride AgTaN2 was investigated on the basis of density-functional theory using the generalized-gradient approximation (GGA). AgTaN2 is predicted to be a semiconductor with an indirect band gap. The characters of the top of the valence band and the bottom of the conduction band are attributed to Ag-N antibonding and Ta-N antibonding interactions, respectively. These results were compared to the bonding situation in isostructural AgGaO2. With increasing pressure, the electronic structure of AgTaN2 changes. At a pressure of ca. 42 GPa, the indirect band gap should transform into a direct one, and at even higher pressures (above 65 GPa) AgTaN2 should become metallic. (C) 2011 The Ceramic Society of Japan. All rights reserved.
  • Akira Miura, Michael Lowe, Brian M. Leonard, Chinmayee V. Subban, Yuji Masubuchi, Shinichi Kikkawa, Richard Dronskowski, Richard G. Hennig, Hector D. Abruna, Francis J. DiSalvo
    JOURNAL OF SOLID STATE CHEMISTRY 184 1 7 - 11 2011年01月 [査読有り][通常論文]
     
    A new silver nitride, AgTaN2, was synthesized from NaTaN2 by a cation-exchange reaction, using a AgNO3-NH4NO3 flux at 175 degrees C Its crystal structure type is delafossite (R (3) over barm) with hexagonal lattice parameters of a=3.141(3) angstrom, c=18.81(2) angstrom, in which silver is linearly coordinated to nitrogen. Energy dispersive X-ray analysis and combustion nitrogen/oxygen analysis gave a composition with atomic ratios of Ag:Ta:N:O as 1.0:1.2(1):2.1(1):0.77(4), which is somewhat Ta rich and indicates some oxide formation. The X-ray photoelectron spectroscopy analysis showed a Ta- and O-rich surface and transmission electron microscope observation exhibited aggregates of ca. 4-5 nm-sized particles on the surface, which are probably related to the composition deviation from a AgTaN2. The lattice parameters of stoichiometric AgTaN2 calculated by density functional theory agree with the experimental ones, but the possibility of some oxygen incorporation and/or silver deficiency is not precluded. (C) 2010 Elsevier Inc. All rights reserved.
  • Akira Miura, Michele E. Tague, John M. Gregoire, Xiao-Dong Wen, R. Bruce van Dover, Hector D. Abruna, Francis J. DiSalvo
    CHEMISTRY OF MATERIALS 22 11 3451 - 3456 2010年06月 [査読有り][通常論文]
     
    Although platinum and platinum-based intermetallic alloys have been extensively studied as catalysts for proton exchange membrane fuel cells, platinum-based nitride catalysts have been relatively unexplored. We report the synthesis and characterization of a platinum-based nitride, Pt(2)Mo(3)N, using a composition spread thin-film deposition technique. The Pt(2)Mo(3)N thin film was generated by codeposition of platinum and molybdenum and subsequent heat treatment in an ammonia flow at 800 degrees C for 6 h. The thin film was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical tests, including the assessment of catalytic activity toward the oxidation of methanol and formic acid and the reduction of oxygen. The nitride film was smooth and contained single-phase, nearly stoichiometric Pt(2)Mo(3)N. Cyclic voltammograms of Pt(2)Mo(3)N in 0.1 M H(2)SO(4) demonstrated electrochemical stability far greater than that of a PtMo alloy with the same Pt:Mo ratio, indicating that the formation of the nitride phase enhances electrochemical stability. The ternary nitride exhibited oxidation currents in formic acid and methanol solutions above approximately 0.0 and 0.4 V vs an Ag/AgCl reference electrode, respectively. These are above the expected equilibrium oxidation potentials of approximately -0.2 V. The onset potential for oxygen reduction was estimated to be similar to 0.2 V vs Ag/AgCl, well below the equilibrium value of 1.0 V.
  • Akira Miura, Xiao-Dong Wen, Hideki Abe, Grace Yau, Francis J. DiSalvo
    JOURNAL OF SOLID STATE CHEMISTRY 183 2 327 - 331 2010年02月 [査読有り][通常論文]
     
    Non-stoichiometric FexWN2 (x similar to 0.72) was synthesized via leaching of Fe from layer-structured stoichiometric FeWN2 by soaking in Sulfuric acid at ca. 50 degrees C. The synthesized products were characterized by powder X-ray diffraction (pXRD), secondary electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and magnetic measurements. Non-stoichiometric FexWN2 has the same symmetry unit cell as stoichiometric FeWN2 (P6(3)/mmc), but the lattice parameters change: the a-axis expands by 0.16% while the c-axis decreases by 1.5%. Polycrystalline powder of FexWN2 showed similar morphologies as those of FeWN2. The calculated electronic structure of stoichiometric FeWN2 shows a more ionic-bonding character between Fe and N than that between W and N, which presumably allows for the partial Fe leaching from between the W-N prismatic layers. The magnetic susceptibility of FexWN2 smoothly decreases with increasing temperature from 3 to 300 K, unlike the broad maximum seen near 27 K in stoichiometric FeWN2. (C) 2009 Elsevier Inc. All rights reserved.
  • Shiro Shimada, Hiroki Otani, Akira Miura, Takashi Sekiguchi, Masaaki Yokoyama
    JOURNAL OF CRYSTAL GROWTH 312 3 452 - 456 2010年01月 [査読有り][通常論文]
     
    GaN powders doped with varying amounts of Zn were deposited on silica glass substrates at 1160 degrees C by reaction for 1 h of NH3 with gaseous Ga2O and Zn. These precursor gases were produced by reaction of C with Ga2O3 and ZnO, respectively, called carbothermal reduction and nitridation (CRN). For comparison, Zn-doped GaN powders were produced at 1160 degrees C by direct nitridation (DN) of ZnO/Ga2O3 and ZnGa2O4 powders with NH3. Zn-doped GaN single crystals of 1 x 0.5 mm(2) in size were grown in a silica glass crucible by the CRN method. The crystallinity of the GaN powders was determined by X-ray diffraction and their morphology was observed by scanning electron microscopy. The concentrations of 0 and Zn in the GaN powders were determined by the combustion and inductively coupled plasma methods. In-depth profiles of the O, H, and Zn concentrations in the GaN single crystals were determined by secondary ion mass spectroscopy. Cathodoluminescence (CL) observation of the GaN powders was performed to evaluate their quality. It is revealed that, compared with the powders prepared by DN, Zn-doped GaN powders produced by CRN exhibit very high CL intensities at 460 nm due to the presence of Zn. (C) 2009 Elsevier B.V. All rights reserved.
  • Xiao-Dong Wen, Thomas J. Cahill, Roald Hoffmann, Akira Miura
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 131 41 14632 - + 2009年10月 [査読有り][通常論文]
     
    In a theoretical study of a "defect perovskite" structure of stoichiometry AeTiO(2) (AE alkaline earth metal, Be, Mg, Ca, Sr, and Ba), we find substantial Ti-Ti bonding tuned by the size of the Ae(2+) cation. The bonding is one-dimensional, partially a, partially H. These formal d(2) systems are expected to be nonmagnetic and metallic. A competing (for same Ae) structural alternative, an ordered rock-salt structure, is magnetic.
  • Akira Miura, Hongsen Wang, Brian M. Leonard, Hector D. Abruna, Francis J. DiSalvo
    CHEMISTRY OF MATERIALS 21 13 2661 - 2667 2009年07月 [査読有り][通常論文]
     
    Intermetallic PtZn nanoparticles with stable and high activities toward formic acid and methanol electrooxidation were synthesized by reaction of carbon-supported Pt nanoparticles with Zn vapor at 500 degrees C for 8 h under flowing nitrogen at atmospheric pressure. The resulting well-dispersed 3-15 nm diameter PtZn nanoparticles were tetragonal phase (P4/mmm: a = 0.2842(1) nm, c = 0.3488(3) nm) and their Pt:Zn ratio was approximately 1:1. Reactions using unsupported Pt nanoparticles (< 5 nm domain size) produced aggregated masses consisting of 5-60 nm nanoparticles. The catalytic activities of supported PtZn nanoparticles toward formic acid and methanol electrooxidation were studied by differential electrochemical mass spectrometry (DEMS). The intermetallic PtZn nanoparticles exhibited higher currents For both formic acid and methanol oxidation than supported Pt nanoparticles with similar particle sizes, but the activity was not as high as that of PtPb. Finally, we established that vapor phase reactions of nano-Pt and M at temperatures sufficient to produce a vapor pressure of 1 x 10(-4) atm for M are generally successful (M: Bi, Tl, and Pb).
  • J. Takahashi, A. Miura, H. Itoh, K. Sawayama, T. Akazawa, K. Nebuka, H. Miura, M. Kishi
    CERAMICS INTERNATIONAL 34 4 853 - 857 2008年05月 [査読有り][通常論文]
     
    Zn-Mn-Ni-Oxide-based NTC thermistors with variable Ni/Mn ratios were fabricated from powder mixtures of recycled IZC, and commercial MnCO3 and NiCO3. Solid phases and electrical resistivity of each sintered sample were studied as a function of Ni/Mn ratio, sintering temperature and sintering time. At 1200 degrees C for 2 h, samples with the Ni/Mn ratios of 0.38 and higher were found to consist of cubic spinel as a major phase. After sintering at 1250 degrees C for 10 h, densification proceeded with a phase change from cubic spinel to tetragonal one. The electrical resistivity of the samples obtained at 1200 degrees C for 2 h progressively decreased with an increasing Ni/Mn ratio up to 0.38, at which the value became the lowest (4.2 x 10(3) Omega cm, at room temperature) of all the samples fabricated. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
  • Akira Miura, Shiro Shimada, Takashi Sekiguchi, Masaaki Yokoyama, Bunsyo Mizobuchi
    JOURNAL OF CRYSTAL GROWTH 310 3 530 - 535 2008年02月 [査読有り][通常論文]
     
    Highly crystalline gallium nitride (GaN) single crystals with good luminescence property were grown at 1200 degrees C for 2 h by the reaction between Ga2O and NH3 gases flowing into an incised silica crucible. The Ga2O vapor was generated by carbothermal reduction of Ga2O3 at 970 degrees C. The effect of Ga2O generation rate (2-23 mu mol/min) on the morphology, crystallinity, cathodoluminescence property and impurity content was investigated. As the generation rate of Ga2O increased, the crystals changed from prismatic to needle-like shape, with a maximum prismatic crystal size of 1.7 mm x 0.3 min x 0.3 mm at the rate of 15 mu mol/min. The prismatic crystals were found to have high crystallinity by the narrow full-width at a half-maximum (40-70 arcsec) of their (10 (1) over bar0) X-ray rocking curves. Their good luminescence property was indicated by the intense cathodoluminescence peaks centered at similar to 3.47 eV. A relatively high concentration of oxygen (5 x 10(20) atoms/cm(3)) was contained in the crystals, as measured by secondary ion mass spectroscopy. (C) 2007 Elsevier B.V. All rights reserved.
  • Akira Miura, Shiro Shimada, Masaaki Yokoyama, Hiroto Tachikawa, Toshio Kitamura
    CHEMICAL PHYSICS LETTERS 451 4-6 222 - 225 2008年01月 [査読有り][通常論文]
     
    We investigated the properties of heavily oxygen-doped single GaN crystals and proposed their electronic structure based on first-principle calculations. The crystals were grown by carbothermal reduction and nitridation of Ga2O3 at 1180 degrees C for 2-8 h. The crystal were found to have high-crystallinity and high-concentration oxygen (4-9 x 10(20) atoms/cm(3)). Cathodoluminescence measurements of the 8-h-grown crystals showed a shift of band-edge-related luminescence peak toward higher energy (ca. 120 meV). Density of state of oxygen-doped GaN supercell was calculated using the first-principle to support this upward shift of luminescence energy. (C) 2007 Elsevier B.V. All rights reserved.
  • Shiro Shimada, Yoko Miura, Akira Miura, Takashi Sekiguchi
    Crystal Growth and Design 7 7 1251 - 1255 2007年07月 [査読有り][通常論文]
     
    Gallium nitride (GaN) powders doped with various amounts of Ge were deposited at 1000 and 1180 °C on graphite and silica glass substrates by a 1-h reaction of NH3 with gaseous Ga2O and GeO, produced by the reaction of carbon with Ga2O3 and GeO2, respectively. The crystallinity of the GaN powders was determined by X-ray diffraction (XRD) and Raman spectroscopy, and their morphology was observed by scanning electron microscopy. The luminescence of the powders was measured at room temperature by cathodoluminescence (CL) to evaluate the quality of the GaN crystals. The influence of Ge-doping of the GaN powders on their crystallinity, morphology, and luminescence is discussed on the basis of the XRD, Raman spectroscopy, and CL results. It is shown that Ge-doped GaN crystals exhibit very high CL intensities accompanied by the elimination of defect-related emission at 430 nm. © 2007 American Chemical Society.
  • Akira Miura, Shiro Shimada, Takashi Sekiguchi
    JOURNAL OF CRYSTAL GROWTH 299 1 22 - 27 2007年02月 [査読有り][通常論文]
     
    Micrometer- to millimeter-sized wurtzite-type GaN crystals were grown on graphite substrates and at the edge of a silica glass tube at 840-1200 degrees C for 5-120 min by the reaction of NH3 With Ga2O vapor, produced by carbothermal reduction of Ga2O3 powder at 970 degrees C. The GaN crystals were characterized by scanning electron microscopy, optical microscopy, X-ray diffraction, Raman spectroscopy and cathodoluminescence. As the growth temperature and time were increased, the size of crystals grown on the graphite substrate drastically increased from several hundreds nanometer to a few hundred microns with the crystal habits changing from plate to bowtie or hexagonal prism. At the edge of a silica glass tube, the bar-shaped crystals of 1-3 mm, in length were obtained at the 1200 degrees C for 120 min. It was found that carbothermal reduction and high-temperature nitridation of Ga2O3 produced relatively large crystals (similar to 3 min) with better quality. (c) 2006 Elsevier B.V. All rights reserved.
  • Akira Miura, Shiro Shimada
    MATERIALS RESEARCH BULLETIN 41 9 1775 - 1782 2006年09月 [査読有り][通常論文]
     
    GaN crystals were grown on graphite and sapphire substrates at 990-1050 degrees C by reaction of Ga2O with flowing NH3. Ga2O gas was produced at a constant rate (1.3 wt% min(-1)) by reaction of Ga2O3 with carbon at 1000-1060 degrees C. The effect of NH3 concentration (3-100 vol%) and the nature of the substrate on the morphology and orientation of the GaN crystals were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and selected area electron diffraction. It was found that sheet and plate-like crystals grew at different orientations to the substrate with different NH3 concentrations and substrates. (c) 2006 Elsevier Ltd. All rights reserved.

MISC

書籍等出版物

講演・口頭発表等

担当経験のある科目(授業)

  • 固体化学
  • 固体化学北海道大学工学部応用化学科
  • 応用化学への招待北海道大学全学教育科目
  • 工学的創成実験I北海道大学全学教育科目
  • 英語演習[化学系に求められる英語力を身につける]北海道大学全学教育科目
  • 物質構造解析学特論北海道大学大学院総合化学院
  • 化学英語北海道大学工学部応用化学科
  • 応用化学実験II北海道大学北海道大学工学部応用化学科
  • 応用化学演習第二山梨大学大学院工学研究科応用化学専攻
  • 応用化学演習第一山梨大学大学院工学研究科応用化学専攻
  • クリスタルサイエンス山梨大学
  • 応用工学実験I山梨大学工学部先端材料理工学科
  • 基礎ゼミ山梨大学工学部先端材料理工学科
  • 入門化学I山梨大学工学部先端材料理工学科
  • 熱力学演習山梨大学工学部先端材料理工学科
  • 応用化学実験IV山梨大学工学部応用化学科
  • 化学実験山梨大学工学部応用化学科
  • 物づくり発展ゼミ山梨大学工学部応用化学科
  • 物づくり基礎ゼミ山梨大学工学部応用化学科

所属学協会

  • 日本化学会   日本イオン交換学会   電気化学会   日本セラミックス協会   

共同研究・競争的資金等の研究課題

  • 物質輸送の差異を生かした新規準安定相の創出
    科学技術振興機構(JST):さきがけ
    研究期間 : 2021年10月 -2025年03月 
    代表者 : 三浦章
  • アミド化合物を用いた新規三元窒化物材料の創出
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 三浦 章, 長尾 雅則
  • 合成反応設計に基づく新規層状化合物の創出
    日本学術振興会:科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))
    研究期間 : 2020年10月 -2024年03月 
    代表者 : 三浦 章
  • 文部科学省:新学術領域研究(公募)
    研究期間 : 2019年04月 -2020年03月 
    代表者 : 三浦 章
  • 文部科学省:科学研究費補助金(基盤(B))
    研究期間 : 2017年04月 -2020年03月 
    代表者 : 忠永 清治
  • 文部科学省:科学研究費補助金(若手(A))
    研究期間 : 2017年04月 -2020年03月 
    代表者 : 三浦 章
  • 自己燃焼反応による新規モリブデン窒化物の探索
    公益財団法人豊田理化学研究所:豊田理研スカラー
    研究期間 : 2018年04月 -2019年03月 
    代表者 : 三浦 章
  • 文部科学省:科学研究費補助金(基盤(B))
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 水口 佳一
  • 層状炭化物の低温窒化による窒化チタンシートの合成
    日本板硝子材料工学助成会:研究助成
    研究期間 : 2016年04月 -2017年03月 
    代表者 : 三浦 章
  • 文部科学省:科学研究費補助金(挑戦的萌芽)
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 三浦 章
  • NaNH2融液を用いた窒化物ナノ粒子の合成
    矢崎科学技術振興記念財団:国際交流援助
    研究期間 : 2016年06月 -2016年07月 
    代表者 : 三浦 章
  • Ta5N6の結晶構造および電子構造
    日本科学協会:海外発表促進助成
    研究期間 : 2015年08月 -2015年09月 
    代表者 : 三浦 章
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2013年 -2014年 
    代表者 : 三浦 章
  • 色つき水晶の水熱合成による教育研究活動
    日教弘会山梨支部:日教弘会山梨支部奨励金
    研究期間 : 2011年07月 -2012年03月 
    代表者 : 三浦 章
  • Investigation of interlayer reactions in nitrides/carbodiimides by experimental and computational approaches
    Alexander von Humboldt Foundation:Alexander von Humboldt Fellowship
    研究期間 : 2010年02月 -2010年11月 
    代表者 : 三浦 章
  • 炭素熱還元窒化法による大型GaN結晶成長とその特性制御
    北海道大学クラーク財団:博士後期課程研究助成
    研究期間 : 2007年04月 -2007年12月 
    代表者 : 三浦 章
  • 炭素還元窒化法によるGaN:Sn結晶の作製とその電気及び光学特性
    日本科学協会:笹川科学研究助成
    研究期間 : 2006年07月 -2007年03月 
    代表者 : 三浦 章

産業財産権

  • 特願2015-213703:電極活物質、電池及び電極活物質の製造方法  2015年10月
    三浦章, 忠永清治
  • 特願2013-053787:ガラスからメソポーラスシリカを製造する方法  2013年03月
    武井貴弘, 熊田伸弘, 三浦章, 高橋浩幸

社会貢献活動

  • 北海道大学化学系への二日体験入学
    期間 : 2019年07月30日 - 2019年07月31日
    役割 : 講師
  • 北海道大学化学系への二日体験入学
    期間 : 2018年07月30日 - 2018年07月31日
    役割 : 講師
  • さっぽろサイエンスフェスタin北大
    期間 : 2018年03月04日
    役割 : 実演
    主催者・発行元 : 北海道大学女性研究者支援室
  • 北海道大学化学系への二日体験入学
    期間 : 2017年08月04日
    役割 : 講師
  • 北海道大学工学部オープンキャンパス
    期間 : 2016年08月
    役割 : 講師
  • 「結晶材料の新展開」 文部科学省ミュージアム「情報ひろば」企画展示
    期間 : 2014年08月01日 - 2014年08月31日
    役割 : 運営参加・支援
    主催者・発行元 : 山梨大学
  • センター見学
    期間 : 2011年 - 2014年
    役割 : 運営参加・支援
    主催者・発行元 : 山梨大学 クリスタル科学研究センター
  • 一日体験化学教室
    期間 : 2010年 - 2014年
    役割 : 講師
    主催者・発行元 : 山梨大学
  • クリスタル科学研究センター公開
    期間 : 2011年 - 2013年
    役割 : 運営参加・支援
    主催者・発行元 : 山梨大学 クリスタル研究センター
  • クリスタル体験講座
    期間 : 2011年 - 2013年
    役割 : 実演
    主催者・発行元 : 山梨大学 クリスタル研究センター

その他

  • 2019年11月 - 2019年11月  6大学助教を対象とした リーダー的素養を学び合う交流会(助教交流会)
  • 2017年07月 - 2017年07月  安全保障輸出管理FD
  • 2016年11月 - 2016年11月  アクティブ型授業への転換を目指して
  • 2016年08月 - 2016年08月  北海道大学工学部オープンキャンパス
  • 2016年08月 - 2016年08月  研究者のためのスキルアップセミナー 
    「外部資金獲得のためのレイアウトとデザイン」についてのスキルアップセミナーを受講した。
  • 2015年09月 - 2015年09月  第27回北海道大学教育ワークショップ(2日間) 
    シラバスの構成法を中心としたワークショップを受講した。
  • 2015年03月 - 2015年03月  Nature Masterclasses受講(2日間) 
    Nature Masterclassesを受講し、論文執筆手法を学習した。
  • 2014年10月 - 2014年10月  ファシリテーション講習を受講(3日間) 
    ファシリテーションの基礎技術を習得した。


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