Defect chemistry and electrical properties of titanium dioxide. 1. Defect diagrams

The present work reports defect diagrams showing the effect of oxygen activity on the concentration of both electronic and ionic defects in TiO2 and its solid solutions with donor- and acceptor-type ions. These diagrams were determined by using defect equilibrium constants related to defect reactions describing the formation of defects. A good agreement between the derived diagrams and defect-related experimental data, including electrical conductivity and thermoelectric power, was revealed. These diagrams may be used for the selection of the optimal processing conditions, including oxygen activity, temperature, and the concentration of aliovalent ions, in order to obtain TiO2 with controlled semiconducting properties that are desired for specific applications.