A high-resolution transmission electron microscopic study was made of the atomistic structure of a Σ = 3 (111) grain boundary. Quantitative evaluation of the high-resolution transmission electron microscopic images revealed that shear stresses, which arose from processing or external loading, had an appreciable effect upon the translation state of the 2 adjacent grains and upon the ionic positions at the grain boundary. Under a low shear stress, the boundary exhibited mirror symmetry with respect to the boundary plane, and a comparatively large free volume. The minimum spacing between Ti ions in the {111} layers which neighbored the boundary plane caused an expansion of 0.06nm with respect to the geometrical model. On the other hand, a high shear stress (of the order of 740MPa) transformed the structure into a so-called lock-in configuration which had no mirror symmetry and a smaller excess volume. This demonstrated that shear stresses could have an important effect upon the atomistic structure of the grain boundaries. Such a change in structure could alter the free energies which were associated with the formation of point defects, and thus influence charge accumulation on the boundary plane; as well as the corresponding space-charge layers.

O.Kienzle, F.Ernst: Journal of the American Ceramic Society, 1997, 80[7], 1639-44