We have studied the chemical, structural and transport properties of a series of In2O3 based samples with germanium doping (from 0 to 15 atom). X-ray diffraction and scanning electron microscopy studies show that the solubility limit of Ge in In2O3 is very small and that additions of more than about 0.5 atom Ge lead to the presence In2Ge2O7 inclusions. The electrical conductivity is strongly enhanced by Ge doping with best values exceeding 1200 S cm(-1) at room temperature. On the other hand, the thermopower decreases with Ge addition, but the thermoelectric power factor remains higher than that of undoped In2O3 and is close to 1mW m(-1) K-2 at 1100 K in In1.985Ge0.015O3. The thermal conductivity is strongly reduced by Ge additions. The dimensionless figure of merit ZT reaches 0.1 at 1273 K in In2O3 and exceeds 0.45 at 1273 K in composite compounds with nominal composition In1.8Ge0.2O3. (c) 2008 Elsevier Ltd. All rights reserved.
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