Thermoelectric properties of Mo-doped bulk In2O3 and prediction of its maximum ZT

Abstract

In a search for new thermoelectric materials, indium oxide (In2O3) was selected as a candidate for high-temperature thermoelectric oxide materials due to its intrinsically low thermal conductivity (<2 W/mK) and ZT values around 0.05. However, low electrical conductivity is a factor limiting the thermoelectric performance of this oxide, and was addressed in this study by Mo doping. It was found that Mo is soluble in In2O3 but forms secondary phases at a fraction near x = 0.06 and higher. Mo was found to be unsuitable for heavy n-type doping necessary to improve the thermoelectric performance of the oxide to the desired level (ZT = 1). However, the experimental data enabled us to analyze the electrical conductivity behavior and the Seebeck coefficient of doped In2O3 with different carrier concentrations, predicting a theoretically achievable maximum power factor value of 1.77 × 10−3 W/mK2 at an optimum carrier concentration. This estimation predicts the highest ZT value of 0.75 at 1073 K, assuming the lattice thermal conductivity value remaining at an amorphous level.