The Influence of Air and Subsequent Vacuum Thermal Treatment on the Thermoelectric Properties of Extruded TiO2 Ceramics

The thermoelectric properties of air sintered and vacuum annealed TiO2 samples consolidated by the extrusion process have been studied. The samples were sintered in air at 1100, 1175, 1250 and 1350 °C and subsequently annealed under vacuum at 1075 °C. After both thermal treatments oxygen deficient phases were not observed and only a single rutile TiO2 phase was present in the samples. The density and grain size of the samples increased with an increase in air sintering temperature, while the total porosity decreased. Electrical conductivity of the samples increased with an increase in air sintering temperature. The highest Seebeck coefficient (~410 μV/K) and thermoelectric power factor (3,25 × 10-6 W/m-1K-2) at 280 °C were obtained for the sample that was sintered in air at 1175 °C before the following annealing under vacuum