Space Charge Segregation at Grain Boundaries in Titanium Dioxide: I, Relationship between Lattice Defect Chemistry and Space Charge Potential

The electrical potential difference between the interface and the bulk in TiO 2 is obtained as a function of temperature, oxygen pressure, and acceptor or donor doping from a space charge model that explicitly includes the high‐temperature lattice defect chemistry. Using defect equilibrium constants for TiO 2 from previous literature studies, it is shown that for a space charge determined by ionic defect equilibration with the interface, the potential is negative in undoped and acceptor‐doped TiO 2 and positive at high donor concentrations. The isoelectric point lies in the donor‐doped regime at high temperatures due to the contribution of defects from reduction, even for fairly oxidizing ambients.