Phase transformation of poled "chem-prep" PZT 95/5-2Nb ceramic under quasi-static loading conditions.

Specimens of poled 'chem-prep' PNZT ceramic from batch HF803 were tested under hydrostatic, uniaxial, and constant stress difference loading conditions at three temperatures of -55, 25, and 75 C and pressures up to 500 MPa. The objective of this experimental study was to obtain the electro-mechanical properties of the ceramic and the criteria of FE (Ferroelectric) to AFE (Antiferroelectric) phase transformations so that grain-scale modeling efforts can develop and test models and codes using realistic parameters. The poled ceramic undergoes anisotropic deformation during the transition from a FE to an AFE structure. The lateral strain measured parallel to the poling direction was typically 35 % greater than the strain measured perpendicular to the poling direction. The rates of increase in the phase transformation pressures per temperature changes were practically identical for both unpoled and poled PNZT HF803 specimens. We observed that the retarding effect of temperature on the kinetics of phase transformation appears to be analogous to the effect of shear stress. We also observed that the FE-to-AFE phase transformation occurs in poled ceramic when the normal compressive stress, acting perpendicular to a crystallographic plane about the polar axis, equals the hydrostatic pressure at which the transformation otherwise takes place