Electrical properties of polycrystalline TiO2.: Thermoelectric power

The present work determined thermoelectric power for high-purity polycrystalline TiO2 at elevated temperatures (1,123-1,323 K) and in the gas phase of controlled oxygen activity, 10(-13) Pa < P(O-2) < 10(5) Pa. The slope of the thermoelectric power vs log p(O-2) is 1/10, instead of 1/6 expected by the theory and observed for TiO2 single crystal. The discrepancy between the two is considered in terms of the effect of the local grain boundary structure on thermoelectric power. A comparison between the electrical conductivity and thermoelectric power data indicates that the oxygen activity values related to the n-p transition point determined by thermoelectric power are lower than those determined by electrical conductivity.