Measurements of both electrical conductivity and thermoelectric power were used to monitor the equilibration kinetics of undoped single-crystal TiO2 during prolonged oxidation at 1123 and 1323K and p(O2) = 75kPa. Two kinetics regimes were revealed: kinetics regime I (rapid kinetics), which was rate-controlled by the transport of oxygen vacancies, and kinetics regime II (slow kinetics), which was rate-controlled by the transport of titanium vacancies. The incorporation of titanium vacancies allows undoped p-type TiO2 to be processed in a controlled manner. The kinetics data were used to determine the chemical diffusion coefficient (Dchem) associated with the transport of titanium vacancies, which was equal to Dchem = 8.9 x 10-14m2/s and Dchem = 9.3 x 10-15m2/s at 1323 and 1123K, respectively.

Electrical Properties and Defect Chemistry of TiO2 Single Crystal. IV. Prolonged Oxidation Kinetics and Chemical Diffusion. Nowotny, M.K., Bak, T., Nowotny, J.: Journal of Physical Chemistry B, 2006, 110[33], 16302-8