Grain-boundary plane orientation dependence of electrical barriers at Σ5 boundaries in SrTiO₃

Dependence of the electrical properties on grain-boundary plane orientation is examined by a combination of high-resolution transmission electron microscopy, impedance spectroscopy, and electron energy-loss spectrometry using two kinds of SrTiO₃ Σ5 ([1 0 0]/36.8°) bicrystalline grain boundaries: symmetric (3 1 0) (18.4°/18.4°) and asymmetric (8.4°/28.4°). While the symmetric grain boundary is observed to be straight with the symmetric (3 1 0)//(3 1 0) plane orientation, the asymmetric grain boundary is faceted into symmetric (3 1 0)//(3 1 0) and (2 1 0)//(2 1 0), and asymmetric (1 0 0)//(4 3 0). Grain-boundary impedance is observed only in the asymmetric grain boundary, and the electron energy-loss spectrometry quantification indicates that the asymmetric (1 0 0)//(4 3 0) facets are more oxygen-deficient than the symmetric ones. The results suggest that the asymmetric (1 0 0)//(4 3 0) facets are the most resistive among the three different facets.