Poling of soft piezoceramic PZT

The properties of piezoelectric ceramic materials are strongly dependent on the degree of polarization as set by the poling process. In the present work a soft piezoceramic PZT material was polarized at different poling conditions. The hysteresis loop, the polarization current and pyroelectric current measurements were used to evaluate the polarization state of the material. The hysteresis loop was monitored using a home-made computer controlled Sawyer–Tower circuit. The polarization current was recorded during the poling process at different applied electric fields, poling time and temperature. The pyroelectric coefficient and the polarization were calculated from the pyroelectric current. The polarization calculated from these data was in excellent agreement with the polarization as calculated from the poling current. The relative permittivity and loss factor were measured as a function of temperature after different poling conditions. The effects of the various poling conditions on the dielectric and ferroelectric properties of the soft PZT are discussed. It is shown that, contrary to common practice, poling at a field slightly larger than the coercive field is adequate to reach full polarization at room temperature.