Synthesis and post-annealing effects on the transport properties of thermoelectric oxide (ZnO)mIn2O3 ceramics

The synthesis and transport properties of n-type thermoelectric oxide (ZnO)mIn2O3 (ZmIO) ceramics prepared by conventional solid-state reaction method have been reported. It is found that the transport properties of ZmIO ceramics are very sensitive to the post-annealing temperature as well as the zinc content m. The resistivity of Z5IO annealed at 1400 °C decreases by more than 2 orders of magnitude in comparison with that of Z5IO annealed at 1200 °C, while the resistivities of Z6IO compounds annealed at 1250 and 1350 °C are more than 3 orders of magnitude larger than that of Z6IO annealed at 1300 °C. All the ZmIO compounds annealed at 1300 °C show electron-type conduction with a lowest resistivity at m = 6. It is suggested that the oxygen defects or vacancies in the InO2 layers play a major role on the carrier scattering mechanism, and the observed temperature-dependent resistivity for Z5IO and Z6IO compounds can be satisfactorily described by the variable-range hopping conduction. Furthermore, it is found that the values of Seebeck coefficient for ZmIO are also very sensitive to the zinc content m. The dimensionless figure of merit of 0.0045 at 300 K for m = 6 has been obtained.