Nonstoichiometry and the electrical activity of grain boundaries in SrTiO3

A combination of experiments and first-principles calculations is used to s how that grain boundaries in SrTiO3 are intrinsically nonstoichiometric. To tal-energy calculations reveal that the introduction of nonstoichiometry in to the grain boundaries is energetically favorable and results in structure s that are consistent with atomic-resolution Z-contrast micrographs. Electr on energy-loss spectra provide direct evidence of nonstoichiometry. These r esults and calculations for nonstoichiometric grain boundaries provide an e xplanation of the microscopic origin of the "double Schottky barriers" that dominate the electrical behavior of polycrystalline oxides.