Experimental investigation of non-linear constitutive behavior of PZT piezoceramics

Abstract

The uni-axial non-linear large signal behavior of PIC 151 soft PZT ceramics was experimentally investigated under a pure electric field, a pure compressive stress and combined electromechanical loading conditions, respectively. Polarisation and strain vs. E field hysteresis loops were observed under a pure cyclic electric field load. The corresponding strain vs. polarisation (S - P) curves also exhibited a significant hysteresis. The material response was found to depend on the loading rate and amplitude of the applied E field. A higher loading rate resulted in a smaller coercive field. Ageing effects caused the remnant polarisation and strain to decrease with time after removing the E field load. As subjected to a pure compressive stress load, the material exhibited non-linear stress-strain behavior. In addition, a non-linear depolarisation curve was observed for the pre-poled specimen. Permanent changes of polarisation and strain induced by the mechanical load could be brought back to their initial values by a subsequent application of an electric field to repolarise the material. Loading rate dependence was also found in the non-linear stress - strain behavior. When being subjected to a constant load, this material exhibited significant time-dependent effects. Polarisation and strain exhibited creep-like behavior with the passage of the external load hold time. Most pronounced time-dependent effects were observed as the load was close to the coercive field or the coercive stress. Polarisation and strain versus electric field hysteresis loops were measured under various levels of a preload compressive stress. It turned out that the superimposed compression load reduced the remnant polarisation, decreased the coercive field and also had a significant impact on the dielectric and piezoelectric properties. High field dielectric permittivity and piezoelectric coefficients were found to be enhanced by the compressive preload within a small range. The improved performance was accompanied by an unfavorable larger hysteresis, which was attributed to larger extrinsic contribution due to more non-180° domain switching induced by the prestress. The effects of a bias electric field on the non-linear stress - strain and stress - depolarisation response were also studied. The non-linear curves were effectively closed upon application of an electric field parallel to the pre-poling direction. Larger stresses were needed to initiate and forward the ferroelastic domain switching. The inverse of this trend occurred when the specimen was subjected to a bias electric field anti-parallel to the pre-poling direction.