Electrical properties of niobium-doped titanium dioxide. 3. Thermoelectric power

The present work studied semiconducting properties for polycrystalline specimens of Nb-doped TiO 2 (0.65 atom % Nb) by the measurements of thermoelectric power in the temperature range of 1073-1298 K and in the oxygen activity range of 10 -13 Pa < p(O 2) < 75 kPa. The determined thermoelectric power data allow one to make the following points: (1) The charge transport in Nb-doped TiO 2 is closely related to oxygen activity; (2) in reduced conditions, Nb-doped TiO 2 exhibits metallic-type properties, which are related to electronic charge compensation; (3) in oxidized conditions, Nb-doped TiO 2 exhibits semiconducting properties, which are related to ionic charge compensation; and (4) the thermoelectric power data are consistent with the proposed effect of niobium on the defect disorder model of TiO 2.