Tantalum enrichment in tantalum-doped titanium dioxide

This investigation has assessed the behavior of Ta enrichment in Ta-doped TiO2 under various conditions of controlled oxygen activity and temperature. The aim has been to establish the relationships between specific processing conditions and the resulting compositional variation within the surface and near-surface region. Under the application of oxidizing conditions [p(O2) = 101 kPa], it has been observed that Ta will strongly enrich the surface of Ta-doped TiO2 irrespective of the annealing temperature (over the range of 1173-1523 K). However, under reducing conditions [p(O2) in the vicinity of 10-10 Pa], Ta enrichment is observed at 1173 K, but Ta depletion from the surface and near-surface is observed at 1348 and 1523 K. This is attributed to an apparent lack of stability of the surface phase, which could possibly be TiTa2O7. The results for the investigation contribute to the engineering of TiO2-based photoelectrode materials that possess improved charge separation properties.