On the origin of the large piezoelectric effect in morphotropic phase boundary perovskite single crystals

The high-field behavior of perovskite ferroelectrics close to a morphotropi c phase boundary is investigated using the thermodynamic theory of ferroele ctrics. For Pb(Zr0.55Ti0.45)O-3, a phase transition from the rhombohedral t o the tetragonal state is predicted for a critical field of approximately 4 MV m(-1) parallel to the [001] axis. The transition is characterized by a strain of 0.015 parallel to [001]. It is postulated that this transition is the origin of the large field-induced strains observed in single crystals of complex perovskite solid solutions with morphotropic phase boundaries. I t is proposed that the transition is diffuse with respect to the applied fi eld due to the inhomogeneity of the critical field arising from the B-site disorder in the complex perovskites. A simple random-field model illustrate s the hypothesis. (C) 2000 American Institute of Physics. [S0003-6951(00)02 501-8].