ATOMISTIC STRUCTURE OF SIGMA=3, (111) GRAIN-BOUNDARIES IN STRONTIUM-TITANATE

This paper presents the results of experimental and theoretical studie s on the atomistic structure of Sigma = 3, (111) grain boundaries in S rTiO3 (strontium titanate). By means of high-resolution transmission e lectron microscopy (HRTEM) we have imaged the structure of such gain b oundaries in cross-sectional view, using specimens that we prepared fr om a macroscopic SrTiO3 bicrystal. By quantitative evaluation of HRTEM images that we recorded along the common [110] direction of the two a djoining half crystals we hale determined the positions of the atom (i on) columns near the grain boundary plane with an average precision of 0.015 nm. We compare the experimental structure with model structures we have obtained by molecular statics calculations, employing empiric al potentials. The equilibrium structure obtained bg thf calculations reproduces the characteristic features of the experimental grain bound ary structure. Concerning the atom positions close to the grain bounda ry plane. however, the theoretical structure and the experimental stru cture exhibit significant discrepancies, which we discuss at the end o f this paper.