Thermodynamic nature of phase transitions in Pb(ZrxTi1-x)O-3 ceramics near the morphotropic phase boundary .2. Dielectric and piezoelectric studies

From a study of the temperature dependence of the dielectric constant of Pb(ZrxTi1-x)O-3 the ferroelectric transition for 0.515 less than or equal to 0.535 is shown to be discontinuous in nature while it is continuous for x = 0.550. It is proposed that there may be a tricritical point around x = 0.545. The two-phase nature of the morphotropic phase boundary (MPB) has been confirmed from the temperature dependence of the resonance frequency. The temperature variation in the planar coupling coefficient k(p) is correlated with structural changes to show that the maximum k(p) at a given Zr concentration x is a function of temperature T and occurs in the tetragonal phase field just outside the two-phase MBP region in the (x,T) plane.