Lattice strain visualization inside a 400 nm single grain of BaTiO 3 in polycrystalline ceramics by Bragg coherent X-ray diffraction imaging

The degree of anisotropy and the domain arrangement of crystal structures in ferroelectrics are affected by the grain boundaries and by the shape and size of the grains. To understand the grain boundary effects that occur in ferroelectric ceramics, we introduce a technique for nondestructively observing the internal lattice strain distribution of a submicrometer-sized ferroelectric grain in polycrystalline materials. The ferroelectric phase transition of a single grain in the polycrystalline materials was evaluated by tracking the changes in the Bragg coherent X-ray diffraction (CXD) patterns. The internal lattice strain distribution of the grains in the paraelectric phase was visualized via Bragg CXD imaging. A pair of 90° domains in the ferroelectric phase were also imaged in three dimensions, and showed a domain boundary correlated with the internal lattice strain caused by the stresses from the adjacent grains.