A 20-resolved hadox study of batio 3

The previous experiment of high-angle double-crystal X-ray diffraction (HADOX) on the cubic-to-tetragonal transition in BaTiO₃ has been extended. It is confirmed with a higher degree of accuracy that the tetragonal crystal consists of several grains at the transition. The lattice constants are the same for all the grains; the directions of the crystallographic axes of the grains are scattered in a limited angular range. The size and orientation of the grains are random. It is found that the lattice constant of the cubic crystal in the state of two-phase coexistence is more sensitive to the temperature than in the state of the pure cubic phase. The results of the grain and crystal orientations are discussed in terms of the relaxation of stresses.