A theory for structural phase transitions in BaTiO3 single crystal and PbZrO3 -xPbTiO3 solid solution

A phenomenological theory has been proposed for the diffusionless structuralphase transitions in BaTiO3single crystal and PbZrO3 -xPbTiO3 solid solution here. It has been found that for BaTiO3single crystal, both the phase transitionsand the crystal structurescan be predicted with the crystalline anisotropy constants and strain constants that depend on the temperature. For PbZrO3 -xPbTiO3 solution, the morphotropic phase boundaries arise from the strong dependence of the crystalline anisotropy constants on the composition. The good agreement between the numerical results and experimental observations has shown that our theory is effective for the diffusionless structuralphase transitions.