The effects of nonhydrostatic compression and applied electric field on the electromechanical behavior of poled lead zirconate titanate 95/5–2Nb ceramic during the ferroelectric to antiferroelectric polymorphic transformation

We conducted hydrostatic compression and constant-stress-difference experiments, with and without an applied electric field, on poled, niobium-doped lead zirconate titanate ceramic. The objective was to quantify the effects of nonhydrostatic stress and electric field bias on electromechanical behavior of the ceramic during the ferroelectric, rhombohedral → antiferroelectric, orthorhombic phase transformation. Increasing stress difference (shear stress) decreases the mean stress at which the transformation occurs. Increasing shear stress also retards the rate of transformation, causing reductions in both the rate of charge release and peak voltage attained during depoling. Application of the electric field bias slightly increases the transformation pressure for poled ceramic. Previously, we showed that under nonhydrostatic stress, the transformation took place in unpoled ceramic when the maximum compressive stress equalled the hydrostatic pressure at which the transformation would otherwise occur. This simple stress criterion does not apply to poled ceramic. However, poled material has a preferred crystallographic orientation and mechanical anisotropy, whereas unpoled ceramic is isotropic. We present a qualitative model for the transformation under nonhydrostatic stress-related to that anisotropy, which resolves these seemingly disparate observations.