The focal-series reconstruction technique of high-resolution electron microscopy was used to make a precise determination of the spacings between atomic columns at a Σ = 3 {111} twin boundary in the perovskite. It was found to be possible to detect a predicted expansion of the nearest Ti-Ti spacing across the boundary plane. In addition, there was a contraction of the nearest BaO-BaO spacing. Direct visualization of O columns in the boundary plane was demonstrated. The boundary structure agreed in detail with a sub-unit of the hexagonal phase.

Investigation of Atomic Displacements at a Σ3 {111} Twin Boundary in BaTiO3 by Means of Phase-Retrieval Electron Microscopy. C.L.Jia, A.Thust: Physical Review Letters, 1999, 82[25], 5052-5