Thermoelectric power in reduced pure and Nb-doped TiO2 rutile at high temperature

The nature of defects in reduced pure and Nb-doped TiO2 rutile is investigated at high temperature by Seebeck coefficient measurements. The classical point defect model approach allows a good fit of the theoretical curves to experimental data. In undoped rutile, the main defects should be titanium interstitials in a large oxygen partial pressure range. For small departures from stoichiometry, the influence of impurities and band to band thermal excitation is discussed. In the case of Nb-doped rutile, two kinds of compensation may occur. Some conclusions related to transport phenomena in such materials are drawn.