X-ray white beam topography of self-organized domains in flux-grownBaTiO3single crystals

Abstract

The phenomenon of self-organization of domains into a ``square-net pattern'' in single-crystal, flux-grown $\mathrm{BaTi}{\mathrm{O}}_{3}$ 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\ifmmode^\circ\else\textdegree\fi{} $a$ and $c$ domains in the projection topographs, and shows a rapid decrease towards 110 \ifmmode^\circ\else\textdegree\fi{}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 ${\ensuremath{\alpha}}_{100}=8.1(\ifmmode\pm\else\textpm\fi{}0.3)\phantom{\rule{0.16em}{0ex}}\mathrm{mrad}$ is at a maximum and corresponds to the radius of curvature of the surface being 16.3(\ifmmode\pm\else\textpm\fi{}0.6) mm.