EFFECT OF SHEAR-STRESS ON THE ATOMISTIC STRUCTURE OF A GRAIN-BOUNDARYIN STRONTIUM-TITANATE

We have studied the atomistic structure of a Sigma 3 (111) grain bound ary in strontium titanate by high-resolution transmission electron mic roscopy (HRTEM), Quantitative evaluation of HRTEM images reveals that shear stresses, which may originate from processing or external loadin g, have an important effect oh the translation state of the two adjace nt grains and on the ion positions at the grain boundary. While under low shear stress the boundary exhibits mirror symmetry with respect to the boundary plane and a comparatively large free volume, high shear stress transforms the structure to a ''lock-in'' configuration, which has no mirror symmetry and a smaller excess volume, These results sugg est that internal or external stresses may significantly alter the cha rge transport properties of SrTiO3.