Ferroelectrics with crystal sizes ranging from a few nanometers to several hundred nanometers (called mesoscale) significantly change their dielectric properties and anisotropy depending on their size and shape. In this article, we track the structural phase transition of a single BaTiO3 grain using coherent X-ray diffraction and successfully visualize the three-dimensional outer shape, the domain arrangement in the tetragonal phase, and the atomic displacement distribution in the cubic phase using Bragg coherent X-ray diffraction imaging (CDI). The Bragg-CDI results suggest that the BaTiO3 grains in the paraelectric phase exhibit grain-boundary slip, inherited from the 90° domain boundary in the tetragonal phase. Structural visualization using coherent X-rays with mesoscale sizes will contribute to our understanding of external effects on the ferroelectricity and dielectric properties of ferroelectric fine crystals.
