Pyroelectric properties of low-coercive PZT-based materials

The temperature dependence of the dynamic pyroelectric coefficient at the sinusoidal thermal flow (f = 2.5; 10 and 800 Hz), the discharge currents and the dielectric permittivity (f = 1 kHz) for three groups of the low-coercive materials was studied. These materials-belong:to the multicomponent PZT-based systems modified with certain additives and have the Curie temperatures 215, 280 and 320 degrees C (compositions 1, 2, 3). It has been established that in the process of heating the sample, in the region of the transition into a paraelectric phase the dynamic pyroelectric coefficient passes through two maxima between which the difference of temperatures is 27.5; 25 and 6 degrees C for compositions 1, 2, 3, respectively. The maxima of discharge currents and the anomalies in the temperature dependence of the dielectronic permittivity correspond to these maxima. A partial depolarization of the samples in the region of a low-temperature:maximum of the pyroelectric coefficient and the discharge current is due to the release of a space charge and the increase of mobility of the domain boundaries in the vicinity of the morphotropic phase transition.