Core Structure of CSL (Coincident-Site-Lattice) Boundaries in NiO

摘要

Atomic resolution electron microscopy is used to study <001> CSL (coincident-site-lattice) tilt boundaries in NiO. Asymmetric as well as symmetric grain-boundary plane orientations are found in bicrystals grown by the Verneuil technique. The sigma = 5, (310) grain boundary is observed to occur in two distinct forms, both of which differ from previously proposed theoretical models. The sigma = 13, (510) boundary, in addition to also showing a multiplicity of structures, is not planar on an atomic scale, but includes displacements of structural units normal to the average grain-boundary plane. It is suggested that the reduced atomic density at high-purity ceramic-oxide grain boundaries is not only due to lattice expansion, but is in part due to a high concentration of Schottky pairs in the grain boundary. 11 refs., 8 figs. (ERA citation 13:024670)