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 microsc opy (TEM) techniques. No cation non-stoichiometry or impurity segregan ts could be detected at the boundary within the limits of the energy d ispersive X-ray microanalysis technique used, while preliminary electr on energy loss spectroscopy analysis reflects that changes in the opti cal/dielectric function or the valence of the cations at the interface are too subtle to be detected with our coarse scale measurements. Hig h-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 t ranslation (RBT). An in-plane RBT of 1/2d(130) (similar to 0.62 Angstr om) is identified from the high-resolution electron micrographs. A sem i-empirical model of the relaxed atomic structure of the grain boundar y based on crystal chemistry principles is proposed, which includes th e observed RBT and individual atomic relaxations at the boundary core.