A Theory for Diffusionless Structural Phase Transitions in BaTiO3 and   PZT Single Crystals
  A phenomenological theory has been proposed for the diffusionless structural phase transitions in crystalline solids here. It has been found that for BaTiO3 single crystal, both the phase transitions and the crystal structures can be predicted with the crystalline anisotropy constants and order parameter dependent strain constants that depend on the temperature. The results have also shown that the morphotropic phase boundaries in PZT crystals arise from the crystalline anisotropy. 
Hui Zhang
cond-mat.mtrl-sci