Development of innovative thermoelectric materials based on the strongly-correlated electron system in transition-metal oxides

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K05019
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: Doshisha University
• Principal Investigator: Kato Masaki 同志社大学, 理工学部, 教授 (90271006)
• Co-Investigator(Kenkyū-buntansha): 廣田 健 同志社大学, 研究開発推進機構, 嘱託研究員 (30238414) ; 道岡 千城 京都大学, 理学研究科, 助教 (70378595)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: パイロクロア / 遷移金属酸化物 / 熱電変換特性 / 化学的圧力効果

Outline of Final Research Achievements

In this study, we apply the quantum critical phenomenon by synthesizing a novel substitution type solid solution for pyrochlore-type transition metal oxides and related transition-metal oxides, which show quantum critical phenomena at the boundary between conductors and insulators. The purpose was to develop new thermoelectric materials. It was confirmed that the thermoelectric properties were exhibited in a novel substitution type solid solution in which Co, Cu, Mn, etc. were substituted with a pyrochlore-type oxide containing ruthenium. Although the dimensionless figure of merit ZT (= S2T / ρκ, S is the Seebeck coefficient, ρ is the electrical resistivity, κ is the thermal conductivity, and T is the absolute temperature) was not found to be high enough, it was clarified that the thermoelectric conversion characteristics are exhibited by performing appropriate carrier doping to the electronic state near the quantum critical point.

Free Research Field

固体化学、物性化学

Academic Significance and Societal Importance of the Research Achievements

遷移金属を含む酸化物セラミックスにおいて，元素置換などにより，結晶構造や遷移金属元素の電子状態を変化させることができる。それによって物質の電気伝導性や磁気特性を制御することができ，特に本研究ではいわゆる強相関電子状態にある遷移金属酸化物において熱電変換特性を発現できることが明らかになった。熱電変換特性のさらなる向上につながる物質開発指針のひとつを明らかにできたことが本研究の意義である。