Thermal Behavior and phase transition in PZT near the morphotropic phase boundary

The heat capacities of single crystals of antiferroelectric PbZrO3 and PbZr0.99Ti0.01O3, and sol-gel derived ceramics of ferroelectric PbZr(1-x)TixO(3) (x = 0.46, 0.48, and 0.50) were measured by a.c. calorimetry. Only one sharp anomaly at 505.6 K in a PbZrO3 single crystal showed the paraelectric-antiferroelectric phase transition without any accompanying intermediate phase. In addition to the antiferroelectric phase transition, PbZr0.99Ti0.01O3 showed two clear anomalies that corresponded to a series of phase transitions. PZT near the morphotropic phase boundary (MPB) showed one peak and additional broad shoulder-type anomalies in C p at high temperatures. The broad shoulder showed very wide thermal hysteresis of about 140 K, which evidence suggests an intermediate state between paraelectric and ferroelectric phases. The monoclinic phase in the low-temperature region reported by Noheda et al. was confirmed.