Phase transition behaviors of PbZr _1-xTi _xO ₃ single crystals as revealed by elastic anomalies and central peaks

Two PbZr _1-xTi _xO ₃ (PZT) single crystals with x ≈ 0.45 and 0.42 near the morphotropic phase boundary were studied by Brillouin light scattering, giving rise to the first single-crystal elastic data which were discussed in terms of the correlation between the acoustic anomalies and the phase transition sequence. The ferroelectric phase transition of PZT with x ≈ 0.45 was second order (or very close to the second order) which accompanied very large polarization fluctuations resulting in the formation of strong central peaks. A revised phase diagram of PZT was suggested including refinement of the tilt phase boundary and a possible existence of tricritical point.