Thermoelectric Performance Enhancement of Vanadium Doped n-Type In2O3 Ceramics via Carrier Engineering and Phonon Suppression

n-Type oxide thermoelectric materials remain challenging for various applications because of their average electrical conductivity, high thermal conductivity, and hence low thermoelectric performance. In this work, we have studied the chemical, structural, and transport properties of vanadium doped In2O3 thermoelectric materials prepared via spark plasma sintering (SPS). The solubility of V in In2O3 is about 6 at % and V4O9 as a secondary phase was observed in 8 at %. V doping leads to a synergistic improvement in electrical conductivity with a simultaneous reduction of the thermal conductivity, yielding ZT = 0.42 at 973 K in In1.88V0.12O3 that is 320% improvement than that of pristine In2O3. This enhancement in electrical conductivity is because of change in charge concentration via pentavalent vanadium doping at the trivalent indium site. The scattering of heat-carrying phonons due to the effects of mass fluctuations and substitutional defects caused by V doping leads to a reduction in heat conduction. Our results suggest that the TE properties of In2O3 can be improved by simultaneously increasing PF and reducing thermal conductivity via V doping.