Electrical properties of polycrystalline TiO_2• 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, 10¹³ Pa < p(O ₂})<10⁵Pa. The slope of the thermoelectric power vs logp(O₂) 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.