Atomic Structure of Symmetric Tilt Grain Boundaries in NiO

Abstract

High-resolution electron microscopy shows the coexistence of several distinct core structures for coincident-site lattice boundaries in NiO bicrystals near $\Sigma =5, \mathrm{}\left(310\right)\mathrm{}$, and $\Sigma =13, \mathrm{}\left(510\right)\mathrm{}$, where $\Sigma$ is the reciprocal density of coincident lattice sites. Lattice expansion perpendicular to the $\Sigma =5\mathrm{}$ grain boundaries is considerably smaller than calculated theoretically. Structural units in boundaries near $\Sigma =13, \mathrm{}\left(510\right)\mathrm{}$ exhibit translations normal to the grain-boundary plane, resulting in a rumpling of the interface on an atomic scale. Our observations suggest the presence of a high concentration of Schottky pairs in the grain boundaries.