Experiments were performed in order to determine the experimental conditions for the formation of {111} twins and related microstructures. The microstructures of samples which consisted of a mixture of (Ba,Sr)TiO3 and 2mol%TiO2 were observed after sintering (1250C, 100h, air). It was found that {111} twins formed only in samples with faceted Ti17Ba6O40 second-phase particles, similar to the case of BaTiO3. In these samples, abnormal grain growth occurred in the presence of the {111} twins. In contrast, no {111} twins formed and no abnormal grain growth occurred in the samples which contained second-phase particles other than Ti17Ba6O40. With increased substitution of Sr for Ba, the aspect ratio of abnormal grains containing {111} twin lamellae reduced. This was attributed to a reduction in the relative stability, of the {111} planes, with Sr substitution.

{111} Twin Formation and Abnormal Grain Growth in Barium Strontium Titanate. B.K.Lee, Y.I.Jung, S.J.L.Kang, J.Nowotny: Journal of the American Ceramic Society, 2003, 86[1], 155-60

Figure 6

Diffusion of O in BaLaxTi1+xO3

(Solid line: x = 0, dotted line: x = 0.001, dashed line: x = 0.005, dot-dash line: x = 0.02)