Electrical properties and defect chemistry of TiO₂ single crystal. IV. Prolonged oxidation kinetics and chemical diffusion

Measurements of both electrical conductivity and thermoelectric power were used to monitor the equilibration kinetics of undoped single-crystal TiO ₂ during prolonged oxidation at 1123 and 1323 K and p(O₂) = 75 kPa. Two kinetics regimes were revealed: kinetics regime I (rapid kinetics), which is rate-controlled by the transport of oxygen vacancies, and kinetics regime II (slow kinetics), which is 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 (D _chem) associated with the transport of titanium vacancies, which is equal to D_chem = 8.9 × 10^-14 m² s ^-1 and D_chemchem = 9.3 × 10^-15 m ² s^-1 at 1323 and 1123 K, respectively.