[10a-N406-1~10] 9.4 Thermoelectric conversion

▼ [10a-N406-1] Temperature Dependence Of Thermoelectric Properties of Ba_1/3CoO₂ Epitaxial Films

〇(M2)LIAO WU¹, YUQIAO ZHANG², XI ZHANG², HAIJUN CHO², HIROMICHI OHTA² (1.IST-Hokkaido Univ., 2.RIES-Hokkaido Univ.)

Keywords:thermoelectric conversion, oxides

Among many kinds of conducting oxides, layered cobalt oxides such as Na_3/4CoO₂ and Ca₃Co₄O₉ have been extensively studied as p-type thermoelectric materials. Based on our own hypothesis that the thermal conductivity of layered cobalt oxides can be reduced by the ion exchange treatment without suppressing the power factor, recently, we found that Ba_1/3CoO₂ shows rather high ZT of 0.11 at room temperature. Here we report the thermoelectric properties of Ba_1/3CoO₂ epitaxial films at elevated temperatures. Although rather high thermoelectric figure of merit, ZT (~1.2 at 800 K for Na_xCoO₂ single crystal) of layered cobalt oxides have been reported thus far, reliable ZT (~0.3 at 700 °C) is quite small as compared to that of chalcogenide such as PbTe. Such inconsistency is often seen in the literatures published in high impact factor journals, probably due to the instability of conducting oxides at elevated temperatures. Therefore, we firstly studied the stability of Ba_1/3CoO₂ epitaxial films at elevated temperatures. Then, we measured the thermoelectric properties of the Ba_1/3CoO₂ epitaxial films at elevated temperatures.