Thermal conductivity clarification of parallel plate structured material with nanometer sized period - Toward realization of high ZT thermoelectric materials -

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H01314
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Inorganic materials/Physical properties
• Research Institution: Hokkaido University
• Principal Investigator: Ohta Hiromichi 北海道大学, 電子科学研究所, 教授 (80372530)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 熱伝導率 / ナノ周期平行平板構造 / 熱電変換 / 性能指数 / 超格子 / 単結晶薄膜 / 層状コバルト酸化物

Outline of Final Research Achievements

In thermoelectric conversion technology that converts heat into electricity, metal oxides (thermally and chemically stable, harmless) are attractive thermoelectric material candidates, but because of their high thermal conductivity, there is a problem that their efficiency is lower than the conventional thermoelectric materials. In this study, in order to experimentally elucidate the effect of the nanoperiodic parallel plate structure on the thermal conductivity, single crystal thin films of metal oxides having a layered structure were prepared, and the thermal conductivity in the directions orthogonal to and parallel to the layer was precisely measured. 1) InGaO3(ZnO)m: It was found that the thermal conductivity of the nanoperiodic parallel plate structure in the plane perpendicular direction is lower than the thermal conductivity of polycrystals. 2) Layered cobalt oxide thin film: It was found that Ba1/3CoO2 thin film shows the highest room temperature figure of merit (ZT = 0.11).

Free Research Field

材料科学

Academic Significance and Societal Importance of the Research Achievements

ナノ周期平行平板構造の面直方向の熱伝導率が、多結晶の熱伝導率よりも低いという、常識を覆す発見は、熱伝導率が低い酸化物を設計するための大きな指針を与えるものである。また、室温熱電変換性能指数（ZT = 0.11）を示すBa1/3CoO2薄膜については、一般に、性能指数ZTは高温になるほど上昇することから，安定で実用的な熱電変換材料の実現が期待され、将来，工場，火力発電所，自動車やコンピュータなどからの廃熱を電気に変えて有効利用する技術に繋がるものである。