High-temperature thermoelectric properties of In2O3-based mixed oxides and their applicability to thermoelectric power generation

Thethermoelectric properties of mixed oxides In2O3·MOx(MOx= Cr2O3, Mn2O3, NiO, ZnO, Y2O3, Nb2O5 SnO2) are investigated in terms of the thermoelectric materials at high temperature. The Seebeck coefficients,S, of all the samples have negative values, and those of In2O3·SnO2 and In2O3·ZnO increase linearly with temperature, attaining values of –90 and –210 µV K–1 at 1000 °C, respectively. The electrical conductivities, σ, of these oxides are significantly high. The power factor S2σ of the oxides has constantly positive temperature coefficients up to over 1000 °C. Rather low thermal conductivities, κ, of the sintered bodies of the oxides,ca. 1.7 W m–1 K–1 at room temperature, lead to the largest value of the thermoelectric figure of merit Z= 0.4 × 10–4 K–1 for M = Sn at 1000 °C, and the Z value increases toward higher temperatures.