ATOMIC-STRUCTURE OF UNDOPED SIGMA=5 SYMMETRICAL TILT GRAIN-BOUNDARY IN STRONTIUM-TITANATE

The atomic structure of a pristine Sigma = 5 grain boundary in SrTiO3 has been investigated using a variety of transmission electron microscopy (TEM) techniques. No cation non-stoichiometry or impurity segregants could be detected at the boundary within the limits of the energy dispersive X-ray microanalysis technique used, while preliminary electron energy loss spectroscopy analysis reflects that changes in the optical/dielectric function or the valence of the cations at the interface are too subtle to be detected with our coarse scale measurements. High-resolution transmission electron microscopy indicates a symmetrical tilt grain boundary with a (130)-type grain boundary plane. The grain boundary has a compact core, with negligible plane-normal rigid body translation (RBT). An in-plane RBT of 1/2d(130) (similar to 0.62 Angstrom) is identified from the high-resolution electron micrographs. A semi-empirical model of the relaxed atomic structure of the grain boundary based on crystal chemistry principles is proposed, which includes the observed RBT and individual atomic relaxations at the boundary core.