X-ray white beam topography of self-organized domains in flux-grown BaTi O3 single crystals

The phenomenon of self-organization of domains into a "square-net pattern" in single-crystal, flux-grown BaTiO3 several degrees below the ferroelectric to paraelectric phase transition was investigated using in situ synchrotron x-ray topography. The tetragonal distortion of the crystal was determined by measuring the angular separation between the diffraction images received from 90° a and c domains in the projection topographs, and shows a rapid decrease towards 110 °C, the onset temperature for self-organization. The onset of self-organization is accompanied by bending of the {100} lattice planes parallel to the crystal surface, which produces a strain that persists up to and beyond the Curie temperature, where the crystal becomes cubic and the self-organized domains disappear. At the Curie point, the bending angle α100=8.1(±0.3)mrad is at a maximum and corresponds to the radius of curvature of the surface being 16.3(±0.6) mm.