Domain configuration and equilibrium size of domains in BaTiO3 ceramics

The domain structures in BaTiO3 ceramics differ from those of single crystals. The spatial configuration of the domains in the ceramics has been derived from etch patterns. All observed etch patterns can be described by two types of domain configurations. Thin layered domains separated by 90 ° walls are piled up to form sloped stacks. Neighboring stacks are bounded by two types of boundaries. One of them is made up of 90 ° and 180 ° domain walls. The other type has a more complex structure which is not free of polarization charge. In this case the pattern accounts for a head to side relation of polarization vectors. Both structures allow the grain, merely by wall motion, to be easily squeezed to arbitrary deformations up to strains of the order of the spontaneous strain. The elastic energy stored in a mixed wall has been estimated. It shows order of magnitude agreement with the energy of the 90 ° walls if the observed domain size is taken into account.