Theory of the Morphotropic Phase Boundary

A Landau theory is presented for the morphotropic phase boundaries in the solid solution system of perovskite-type oxide ferroelectrics. The origin of useful functions of materials located close to the morphotropic phase boundary are attributed to the isotropy of the thermodynamic potential. In the vicinity of the morphotropic phase boundary the electric and the elastic compliances will be extremely large, and the coercive field may become extremely small, due to the instability against the transversal fluctuations.

Keywords:

• Morphotropic Phase Boundary
• Thermodynamic Potential
• Isotropy
• Transversal Instability