Strontium oxide segregation at SrLaAlO4 surfaces

We report observable segregation of strontium oxide at the surface of strontium lanthanum aluminate single-crystals annealed in oxidizing conditions. Electron microscopy imaging and energy-dispersive X-ray spectroscopy showed that Sr and O segregation occurs on strontium lanthanum aluminate surfaces in the form of polycrystalline islands. The appearance of islands on the (100) and other high-free energy surfaces is strongly suggestive of rocksalt SrO formation. The loss of strontium oxide from the bulk is not compensated solely by point defects, but rather by non-stoichiometric stacking faults which locally result in stable perovskite structures.