Influence of porosity on nonlinear mechanical properties of unpoled porous Pb(Zr0.95Ti0.05)O3 ceramics under uniaxial compression

A series of uniaxial compression experiments on unpoled porous lead zirconate titanate Pb(Zr0.95Ti0.05)O3 (PZT95/5) ceramics were performed to investigate the influence of porosity on the mechanical properties, domain switching and phase transformation via non-contact digital image correlation optical technique to measure the full-field strain. Four unpoled PZT95/5 ceramics were fabricated with a range of porosity levels via systematic additions of pore formers. The nonlinear compressive mechanical behaviors of unpoled PZT95/5 ceramics were measured and evaluated as a function of porosity. The nonlinear deformation mechanism of unpoled PZT95/5 ceramics was attributed to domain switching and ferroelectric (FE) to antiferroelectric (AFE) phase transformation processes, which was verified by analyzing the anomalous behavior between axial strain and radial strain. Normalized critical stresses for the onset of domain switching as well as the onset and exhaustion of phase transformation resulted in a very similar linear decrease with increasing porosity. We suggest that a critical macroscopic volumetric strain is needed for the onset of phase transformation that is nearly independent of porosity.