Design and synthesis of thermoelectric oxides with ultralow thermal conductivity by complex cation engineering

• Project/Area Number: 18K13996
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: Keio University
• Principal Investigator: HAGIWARA Manabu 慶應義塾大学, 理工学部(矢上), 助教 (30706750)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Project Status: Discontinued (Fiscal Year 2020)
• Budget Amount: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2020: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2019: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2018: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
• Keywords: 熱電変換 / セラミックス / 複合イオン / 熱伝導 / Aサイト複合ペロブスカイト / ゾルゲル法

Outline of Final Research Achievements

This study aimed to develop n-type thermoelectric oxides with a low thermal conductivity by constructing the A-site of perovskite titanate with a complex cation composed of lanthanum and potassium ions. Semiconductive ceramic samples were obtained by the conventional solid-state synthesis process. It was found that obtained samples have a highly reduced thermal conductivity. A pair distribution function analysis by the reverse Monte Carlo method suggested that a nanometer-scale chemical heterogeneity of lanthanum and potassium ions contributes to the reduced thermal conductivity. It was also showed that doping of barium is effective to increase the electrical conductivity.

Academic Significance and Societal Importance of the Research Achievements

金属や半導体の熱起電力効果を利用した熱電発電は我が国の消費エネルギーの70%近くを占める排熱の有効利用にむけたキーテクノロジーであるが、熱電変換材料としてはこれまで人体への毒性や高温での不安定性などの問題をもつ重金属系の化合物半導体が使われてきた。本研究によって実証された複合カチオンエンジニアリングによる熱伝導率の低減効果を利用すれば、無害かつ化学的に安定な酸化物を用いた熱電変換材料の開発が可能になると期待される。

Research Products

• [Journal Article] Fabrication of Highly Textured Ca3Co4O9 Ceramics with Controlled Density and High Thermoelectric Power Factors (2020)
  • Author(s): Shimonishi Rina、Hagiwara Manabu、Fujihara Shinobu
  • Journal Title: Journal of the European Ceramic Society Volume: 40 Issue: 4 Pages: 1338-1343
  • DOI: 10.1016/j.jeurceramsoc.2019.11.077
  • Peer Reviewed
• [Journal Article] Reactive Templated Grain Growth and Thermoelectric Power Factor Enhancement of Textured CuFeO2 Ceramics (2020)
  • Author(s): Tato Masahiko、Shimonishi Rina、Hagiwara Manabu、Fujihara Shinobu
  • Journal Title: ACS Applied Energy Materials Volume: 3 Issue: 2 Pages: 1979-1987
  • DOI: 10.1021/acsaem.9b02407
  • Peer Reviewed
• [Journal Article] Synthesis of Ca-Co hydroxides and their use in facile fabrication of textured CayCoO2 thermoelectric ceramics (2019)
  • Author(s): Shimonishi Rina、Hagiwara Manabu、Fujihara Shinobu
  • Journal Title: Ceramics International Volume: 45 Issue: 3 Pages: 3600-3607
  • DOI: 10.1016/j.ceramint.2018.11.020
  • Peer Reviewed
• [Presentation] A サイト複合ペロブスカイト型構造に基づく酸化物熱電材料の設計と合成 (2019)
  • Author(s): 萩原学、Sverre M. Selbach、藤原忍
  • Organizer: 第39回電子材料研究討論会
• [Presentation] Controlled Fabrication of Textured and Porous Ca3Co4O9 Ceramics and Their Thermoelectric Property (2019)
  • Author(s): Rina Shimoinshi、Manabu Hagiwara、Shinobu Fujihara
  • Organizer: Materials Research Meeting 2019
  • Int'l Joint Research
• [Presentation] 配向性と気孔率を制御したCa3Co4O9の作製および熱電特性 (2019)
  • Author(s): 下西里奈、萩原学、藤原忍
  • Organizer: 日本セラミックス協会 2019年年会
• [Presentation] CuFeO2セラミックスの粒子配向制御による熱電変換出力因子の向上 (2019)
  • Author(s): 田藤正彦、下西里奈、萩原学、藤原忍
  • Organizer: 日本セラミックス協会 2019年年会
• [Presentation] Fe系水酸化物を用いた反応性テンプレート粒成長法によるCuFeO2配向セラミックスの作製と熱電特性の評価 (2018)
  • Author(s): 田藤正彦、下西里奈、萩原学、藤原忍
  • Organizer: 日本セラミックス協会 第31回秋季シンポジウム
• [Remarks]
  • URL: http://www.applc.keio.ac.jp/~shinobu/