> 概要
高温・空気中でこれまでにない高い変換効率を有する熱電材料を発見した。この物質は(Ca,Sr, Bi)2Co2O5(Co-225)の組成を有する酸化物ひげ状単結晶（ウィスカー）である。600℃以上の高温・空気中におけるCo-225ウィスカーのゼーベック係数Sと電気抵抗率pはそれぞれ200-210 µV/Kと1.4-1.5 mΩ-cmであった。Co-225多結晶体の熱伝導度kを用い見積もった性能指数ZT (= S2T/pk, T; 絶対温度)は600℃以上の温度で最低でも1.2を超えていることが分かった。この酸化物の発見は高温廃熱エネルギーを利用した熱電発電の実現に期待を持たせる。
Abstract
An oxide single crystalline whisker with high thermoelectric properties at high temperature in air has been discovered. The composition of the whisker is (Ca, Sr, Bi)2Co2O5 (abbreviated to Co-225 whisker). Seebeck coefficient S and electrical resistivity p of the whisker are 200-210µ V/K and 1.4-1.5 mΩ-cm at temperatures higher than 600℃, respectively. Using thermal conductivity k of a Co-225 polycrystalline sample, figure of merit ZT (= S2T/ pk, T; absolute temperature) of the Co-225 whisker is estimated over 1.2 at temperatures higher than 600℃. The discovery of the oxide with high thermoelectric performance at high temperature in air leads to the expectation that electric power generation using waste heat from automobiles,factories, and similar sources will be realized in the near future.factories, and similar sources will be realized in the near future.
