Experiments and first-principles calculations were used to show that grain boundaries in this material were intrinsically non-stoichiometric. Total-energy calculations revealed that the introduction of non-stoichiometry into the grain boundaries was energetically favorable and resulted in structures which were consistent with atomic-resolution Z-contrast micrographs. Electron energy-loss spectra provided direct evidence of non-stoichiometry. These results, and calculations of non-stoichiometric grain boundaries, provided an explanation for the microscopic origin of so-called double Schottky barriers which dominated the electrical behavior of polycrystalline oxides.

Nonstoichiometry and the Electrical Activity of Grain Boundaries in SrTiO3. M.Kim, G.Duscher, N.D.Browning, K.Sohlberg, S.T.Pantelides, S.J.Pennycook: Physical Review Letters, 2001, 86[18], 4056-9