Symmetry of High-Piezoelectric Pb-Based Complex Perovskites at the Morphotropic Phase Boundary:I. Neutron Diffraction Study on Pb(Zn1/3Nb2/3)O3–9%PbTiO3

The symmetry was examined using neutron diffraction method on Pb(Zn1/3Nb2/3)O3–9%PbTiO3 (PZN/9PT) which has a composition at the morphotropic phase boundary between Pb(Zn1/3Nb2/3)O3 and PbTiO3. The results were compared with those of other specimens with same composition but with different prehistory. The equilibrium state of all examined specimens is not the mixture of rhombohedral and tetragonal phases of the end members but exists in a new polarization rotation line Mc# (orthorhombic-monoclinic line). Among examined specimens, one exhibited tetragonal symmetry at room temperature but recovered monoclinic phase after a cooling and heating cycle