Effect of oxygen activity on surface composition of in-doped TiO2 at elevated temperatures

The present work reports the effect of oxygen activity on the segregation-induced surface concentration of indium for In-doped TiO2 at different time intervals (5-120 h) of annealing at 1273 K. It is shown that equilibrium segregation of indium in oxidizing conditions, p(O2) = 21 kPa, is established within 20 h. However, annealing in reducing conditions, p(O2) = 10-10 Pa, does not lead to equilibrium segregation due to indium evaporation, which becomes substantial at p(O2) < 102 Pa. In these conditions, annealing results in an initial rise of surface concentration due to segregation and subsequent decrease due to evaporation. These data may be used for the modification of surface vs bulk composition of In-doped TiO2 in a controlled manner.