Singular grain boundaries in BaTiO3 with excess TiO2

Abstract

The shapes and structures of many randomly selected grain boundaries in BaTiO3 with 0.1, 0.3 and 0.5 excess mol% of TiO2 sintered at 1250degreesC have been examined by TEM. Most of the grain boundaries have flat segments that coincide with low index planes of one of the grain pairs. These low index grain boundaries are likely to be singular. Singular boundary segments appear in a variety of shapes. In the 0.1 mol% Ti specimen. {011} boundary planes appear most frequently, while in the 0.5 mol% Ti specimen, {111} boundary planes are dominant. Some grain boundaries show fine steps with low index terraces indicating that they migrate by the lateral movement of the steps. This step growth mechanism is consistent with the observed slow growth of the matrix grains and abnormal growth of a few grains.