Stability and Decomposition of Perovskite-Type Titanates upon High-Temperature Reduction

Controlling the properties of the surface region of ternary perovskite-type titanates is of high importance in the field of future energy and information technologies. A common method to modify the surface of perovskite oxides such as SrTiO3 is annealing under vacuum conditions. Here we show that the local oxygen partial pressure near to the surface plays a crucial role during annealing. While the oxide is found to be macroscopically stable during high-temperature reduction under standard vacuum conditions and only segregation effects on the nanoscale seem to take place, surface decomposition due to incongruent sublimation occurs as soon as an oxygen getter such as Ti is positioned close to the oxide. In consequence, owing to the high volatility of Sr-containing species at very low oxygen pressures, a Sr-depleted TiOx surface layer is formed. This effect might reveal an alternative possibility to tailor composition and structure of perovskite-type titanate surfaces.