Niobium doped Lead Zirconate Titanate (PZT) with a Zr/Ti ratio of 95/5 (i.e., PZT 95/5-2Nb) is a ferroelectric
with a rhombohedral structure at room temperature. A crystal (or a subdomain within a crystal) exhibits a
spontaneous polarization in any one of eight crystallographically equivalent directions. Such a material becomes
polarized when subjected to a large electric field. When the electric field is removed, a remanent polarization
remains and a bound charge is stored. A displacive phase transition from a rhombohedral ferroelectric phase to
an orthorhombic anti-ferroelectric phase can be induced with the application of a mechanical load. When this
occurs, the material becomes depoled and the bound charge is released. The polycrystalline character of PZT
95/5-2Nb leads to highly non-uniform fields at the grain scale. These local fields lead to very complex material
behavior during mechanical depoling that has important implications to device design and performance.
This paper presents a microstructurally based numerical model that describes the 3D non-linear behavior of
ferroelectric ceramics. The model resolves the structure of polycrystals directly in the topology of the problem
domain and uses the extended finite element method (X-FEM) to solve the governing equations of electromechanics.
The material response is computed from anisotropic single crystal constants and the volume fractions of the
various polarization variants (i.e., three variants for rhombohedral anti-ferroelectric and eight for rhomobohedral
ferroelectric ceramic). Evolution of the variant volume fractions is governed by the minimization of internally
stored energy and accounts for ferroelectric and ferroelastic domain switching and phase transitions in response
to the applied loads. The developed model is used to examine hydrostatic depoling in PZT 95/5-2Nb.