A Model for the Bulk Mechanical Response of Porous Ceramics Exhibiting a Ferroelectric‐to‐Antiferroelectric Phase Transition During Hydrostatic Compression
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At ambient conditions a niobium-doped lead zirconate-titanate composition (PZT 95/5-2Nb) is ferroelectric with a rhombohedral structure, but near the boundary for an antiferroelectric phase having an orthorhombic structure. Applying a hydrostatic pressure of about 0.25 GPa causes the unpoled ceramic to undergo a ferroelectric-to-antiferroelectric polymorphic phase transition with a ∼ 0.9% reduction of volume. Voids present in the ceramic produce localized inhomogeneity in the stress field resulting in both a spread of the transformation over a range of pressure and a reduction in the applied pressure at the onset of the transformation with increasing material porosity. A model for a porous ceramic exhibiting a ferroelectric-to-antiferroelectric phase transition that explicitly accounts for the influence of porosity on the bulk mechanical response will be described and compared to measurements of pressure versus volume strain for two ceramics with different porosity.