Pyrochlore lattice system as a high-performance energy conversion material

• Project/Area Number: 16H03848
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Applied materials
• Research Institution: Nagoya University
• Principal Investigator: Okamoto Yoshihiko 名古屋大学, 工学研究科, 准教授 (90435636)
• Research Collaborator: Takenaka Koshi ; Yamakawa Youichi ; Sawa Hiroshi
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥16,120,000 (Direct Cost: ¥12,400,000、Indirect Cost: ¥3,720,000); Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2017: ¥7,020,000 (Direct Cost: ¥5,400,000、Indirect Cost: ¥1,620,000); Fiscal Year 2016: ¥7,540,000 (Direct Cost: ¥5,800,000、Indirect Cost: ¥1,740,000)
• Keywords: 熱電変換材料 / パイロクロア構造 / エネルギー変換材料 / パイロクロア / 熱電変換 / 幾何学的フラストレーション / 熱・エネルギー変換 / 磁場誘起歪 / 熱・エネルギー変換材料 / パイロクロア格子 / 固体冷凍 / フラストレーション / 負熱膨張 / 固体冷凍材料

Outline of Final Research Achievements

We studied thermoelectric properties of pyrochlore-lattice systems with transition metal atoms, which are expected to show high thermoelectric performance due to the geometrical frustration, multiple degrees of freedom, and rattling effects. We focused on the b-pyrochlore oxide CsW2O6 and found that this compound has large thermoelectric power as a metallic system and very small thermal conductivity probably coming from the rattling effect. We also found that Ta4SiTe4 and Nb4SiTe4, where one-dimensional chains form a triangular lattice, show excellent thermoelectric performance exceeding the practical level at low temperatures.

Academic Significance and Societal Importance of the Research Achievements

現在、熱電変換は室温付近における赤外線センサーの冷却などの限定された用途でのみ実用化されている。本研究では、CsW2O6やTa4SiTe4といった物質が、熱電変換の幅広い実用に繋がる次世代の熱電変換材料の有力候補であることを見出した。特に、Ta4SiTe4は現在熱電冷却用の材料として唯一実用化されているBi2Te3系材料が利用できないマイナス50℃以下の低温領域で高い性能を示す点でユニークである。低温領域における各種デバイスの局所冷却や、液化天然ガスの冷熱を利用した発電など、これまで実用化されていない様々な用途の実用に道を拓く成果といえる。

Research Products

• [Journal Article] Ultra-High Magnetic Field Magnetic Phases up to 130 T in a Breathing Pyrochlore Antiferromagnet LiInCr4O8 (2019)
  • Author(s): Masaki Gen, Daisuke Nakamura, Yoshihiko Okamoto, and Shojiro Takeyama
  • Journal Title: Journal of Magnetism and Magnetic Materials Volume: 473 Pages: 387-393
  • DOI: 10.1016/j.jmmm.2018.10.088
  • Peer Reviewed
• [Journal Article] Large thermoelectric power factor in one-dimensional telluride Nb4SiTe4 and substituted compounds (2018)
  • Author(s): Y. Okamoto, T. Wada, Y. Yamakawa, T. Inohara, and K. Takenaka
  • Journal Title: Applied Physics Letters Volume: 112 Issue: 17
  • DOI: 10.1063/1.5023427
  • Peer Reviewed
• [Journal Article] Inelastic Neutron Scattering Study of the Spin Dynamics in the Breathing Pyrochlore System LiGa0.95In0.05Cr4O8 (2018)
  • Author(s): Yu Tanaka, Rafal Wawrzynczak, Manh Duc Le, Tatiana Guidi, Yoshihiko Okamoto, Takeshi Yajima, Zenji Hiroi, Masashi Takigawa, and Goeran J. Nilsen
  • Journal Title: Journal of the Physical Society of Japan Volume: 87 Issue: 7 Pages: 073710-073710
  • DOI: 10.7566/jpsj.87.073710
  • NAID: 210000134889
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Magnetic and Structural Properties of A-Site Ordered Chromium Spinel Sulfides: Alternating Antiferromagnetic and Ferromagnetic Interactions in the Breathing Pyrochlore Lattice (2018)
  • Author(s): Yoshihiko Okamoto, Masaki Mori, Naoyuki Katayama, Atsushi Miyake, Masashi Tokunaga, Akira Matsuo, Koichi Kindo, and Koshi Takenaka
  • Journal Title: Journal of the Physical Society of Japan Volume: 87 Issue: 3 Pages: 034709-034709
  • DOI: 10.7566/jpsj.87.034709
  • NAID: 210000134746
  • Peer Reviewed
• [Journal Article] Classical Spin Nematic Transition in LiGa0.95In0.05Cr4O8 (2017)
  • Author(s): Wawrzynczak R.、Tanaka Y.、Yoshida M.、Okamoto Y.、Manuel P.、Casati N.、Hiroi Z.、Takigawa M.、Nilsen G.J.
  • Journal Title: Physical Review Letters Volume: 119 Issue: 8
  • DOI: 10.1103/physrevlett.119.087201
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Large Thermoelectric Power Factor at Low Temperatures in One-Dimensional Telluride Ta4SiTe4 (2017)
  • Author(s): Takumi Inohara, Yoshihiko Okamoto, Youichi Yamakawa, Ai Yamakage, and Koshi Takenaka
  • Journal Title: Applied Physics Letters Volume: 110 Issue: 18 Pages: 183901-183901
  • DOI: 10.1063/1.4982623
  • Peer Reviewed
• [Journal Article] Magnetic Transitions under Ultrahigh Magnetic Fields of up to 130 T in the Breathing Pyrochlore Antiferromagnet LiInCr4O8 (2017)
  • Author(s): Yoshihiko Okamoto, Daisuke Nakamura, Atsushi Miyake, Shojiro Takeyama, Masashi Tokunaga, Akira Matsuo, Koichi Kindo, and Zenji Hiroi
  • Journal Title: Physical Review B Volume: 95 Issue: 13
  • DOI: 10.1103/physrevb.95.134438
  • Peer Reviewed
• [Journal Article] Thermoelectric Properties of Antiperovskite Calcium Oxides Ca3PbO and Ca3SnO (2016)
  • Author(s): Yoshihiko Okamoto, Akira Sakamaki, and Koshi Takenaka
  • Journal Title: J. Appｌ. Phys. Volume: 119 Issue: 20
  • DOI: 10.1063/1.4952393
  • Peer Reviewed / Acknowledgement Compliant
• [Presentation] A-Site Ordered Cr Spinel Sulfides: Alternating Antiferromagnetic and Ferromagnetic Interactions in the Breathing Pyrochlore Lattice (2018)
  • Author(s): Yoshihiko Okamoto
  • Organizer: The 2nd Asia-Pacific Workshop on Quantum Magnetism
  • Int'l Joint Research / Invited
• [Presentation] Crystal Growth of 5d Transition Metal Compounds: β-Pyrochlore Oxide CsW2O6 and One-Dimensional Telluride Ta4SiTe4 (2018)
  • Author(s): Yoshihiko Okamoto
  • Organizer: International Workshop on New Materials and Crystal Growth
  • Int'l Joint Research / Invited
• [Presentation] βパイロクロア酸化物CsW2O6における三量体形成 (2018)
  • Author(s): 岡本佳比古、三十日陸斗、二木健太、天野春樹、片山尚幸、澤博、播磨尚朝、竹中康司
  • Organizer: 物性研究所短期研究会「量子多体効果が生み出す液晶的電子状態」
• [Presentation] ブリージングパイロクロア格子をもつCrスピネル硫化物の磁性 (2018)
  • Author(s): 岡本佳比古、森政貴、兼松智也、片山尚幸、三宅厚志、徳永将史、松尾晶、金道浩一、矢島健、竹中康司
  • Organizer: 基研研究会「スピン系物理の最前線」
• [Presentation] 低温で高い熱電変換性能を示す一次元テルル化物Ta4SiTe4とNb4SiTe4 (2018)
  • Author(s): 岡本佳比古
  • Organizer: 第3回固体化学フォーラム
  • Invited
• [Presentation] One-Dimensional Telluride Ta4SiTe4 as a High-Performance Thermoelectric Material (2017)
  • Author(s): Yoshihiko Okamoto, Taichi Wada, Yuma Yoshikawa, Takumi Inohara, Youichi Yamakawa, Ai Yamakage, and Koshi Takenaka
  • Organizer: The 6th Toyota RIKEN International Workshop 2017
  • Int'l Joint Research
• [Presentation] Phase Transition in β-Pyrochlore Oxide CsW2O6 (2017)
  • Author(s): Yoshihiko Okamoto, Haruki Amano, Kenta Niki, Rikuto Mitoka, Naoyuki Katayama, Hiroshi Sawa, Yuto Nakamura, Hideo Kishida, and Koshi Takenaka
  • Organizer: International Workshop on Multipole Physics and Related Phenomena
  • Int'l Joint Research
• [Presentation] 低温で高い熱電性能を示す1次元テルル化物Ta4SiTe4 (2017)
  • Author(s): 岡本佳比古、井ノ原拓実、和田泰地、山川洋一、山影相、竹中康司
  • Organizer: 日本物理学会2017年秋季大会
• [Presentation] 複数イオンの秩序による幾何学的フラストレート磁性体の構造・物性制御 (2017)
  • Author(s): 岡本佳比古
  • Organizer: 日本セラミックス協会第30回秋季シンポジウム
  • Invited
• [Presentation] βパイロクロア酸化物CsW2O6の金属絶縁体転移 (2017)
  • Author(s): 岡本佳比古
  • Organizer: 新学術領域「多極子伝導系の物理」トピカルミーティング「強相関多極子系の超伝導」
• [Presentation] β型パイロクロア酸化物CsW2O6単結晶の合成と物性II (2017)
  • Author(s): 二木健太、岡本佳比古、天野春樹、片山尚幸、澤博、中村優斗、岸田英夫、竹中康司
  • Organizer: 日本物理学会第72回年次大会
  • Place of Presentation: 大阪大学
• [Presentation] ブリージングパイロクロア格子をもつスピネル硫化物AA'Cr4S8 (A = Li, Cu, A' = Ga, In)の磁性 (2016)
  • Author(s): 森政貴、岡本佳比古、三宅厚志、徳永将史、松尾晶、金道浩一、竹中康司
  • Organizer: 日本物理学会2016年秋季大会
  • Place of Presentation: 金沢大学
• [Presentation] High-Field Magnetization of Spin-3/2 Breathing Pyrochlore Antiferromagnets (2016)
  • Author(s): Yoshihiko Okamoto, Masaki Mori, Atsushi Miyake, Masashi Tokunaga, Akira Matsuo, Koichi Kindo, Zenji Hiroi, and Koshi Takenaka
  • Organizer: Highly Frustrated Magnetism 2016
  • Place of Presentation: Taipei, Taiwan
  • Int'l Joint Research
• [Presentation] βパイロクロア酸化物CsW2O6の金属絶縁体転移 (2016)
  • Author(s): 岡本佳比古
  • Organizer: 豊田理化学研究所・特定課題研究「多元秩序制御による熱・体積機能の開拓」第4回研究会
  • Place of Presentation: 東京工業大学フロンティア材料研究所
  • Invited
• [Patent(Industrial Property Rights)] 熱電変換材料および熱電変換素子 (2016)
  • Inventor(s): 岡本佳比古、竹中康司、井ノ原拓実
  • Industrial Property Rights Holder: 国立大学法人名古屋大学
  • Industrial Property Rights Type: 特許
  • Filing Date: 2016-12-26