The shapes and structures of randomly selected grain boundaries in BaTiO3 with 0.1, 0.3 and 0.5 excess mol% of TiO2 sintered at 1250C were examined by transmission electron microscopy. Most of the grain boundaries had flat segments that coincided with low index planes of one of the grain pairs. These low-index grain boundaries were likely to be singular. Singular boundary segments appeared in a variety of shapes. In 0.1mol%Ti specimens, {011} boundary planes appeared most frequently. In 0.5mol%Ti specimens, {111} boundary planes were predominant. Some grain boundaries exhibited fine steps, with low-index terraces, indicating that they migrated via lateral movement of the steps. This step-growth mechanism was consistent with an observed slow growth of the matrix grains and the abnormal growth of a few grains.

Singular Grain Boundaries in BaTiO3 with Excess TiO2. Y.K.Cho, D.Y.Yoon: Materials Transactions, 2004, 45[7], 2083-90