Piezoelectric PZT Ceramics

Today, the most important piezoelectric materials that are technologically important are ferroelectric ceramics based on Pb-containing perovskites. They offer the advantages of most ceramic materials such as ease of fabrication, possibility of variable and application-adapted shaping, as well as low-cost manufacturing. In addition, diverse chemical modifications are available in order to tailor the piezoelectric properties to different applications. The precondition, however, is the possibility to impose a unipolar anisotropy into the otherwise macroscopically isotropic ceramic. This is possible only if the spontaneous polarization can be oriented by a poling process using an external electric field for generating a remanent polarization. In addition, the special behaviour in the vicinity of ferroelectric phase transitions promotes extremely high piezoelectric effects, where the intrinsic ones are connected with the dielectric anisotropy and the extrinsic ones with increased domain wall mobility. Especially, in the periphery of the morphotropic phase boundary (MPB) present in a series of Pb-containing perovskites, such as lead-zirconate-titanate (PZT), this effect technically can be used extensively because the MPB in the temperature-composition phase diagram is nearly vertical, what implies nearly temperature independence.