Coexistence States near the Morphotropic Phase Boundary: II. The Scaling of the Free Energy in PbZr1-xTixO3

A model of coexistence states due to the stable and metastable phases near the morphotropic phase boundary in perovskite-type ferroelectrics was proposed on the basis of the Landau--Devonshire free energy with the scaled parameter values in our previous paper [M. Iwata and Y. Ishibashi: Jpn. J. Appl. Phys. 51 (2012) 09LE03]. Here, the scaling method for the Landau--Devonshire free energy is discussed to clarify the correspondence relation between the scaled and real parameter systems. A new set of scaled parameter values for PbZr 1-x Ti x O 3 (PZT) is proposed on the basis of the real parameters reported by Haun et al. [Ferroelectrics 99 (1989) 45]. Using our scaled parameter values, the stable and metastable regions in the tetragonal and rhombohedral phases under equilibrium in PZT are clarified.