Phase transformation of PZST-86/14-5-2Nb ceramic under quasi-static loading conditions.

Abstract

Specimens of poled and unpoled PZST ceramic were tested under hydrostatic loading conditions at temperatures of -55, 25, and 75°C. 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 of the PZST ceramic to aid grain-scale modeling efforts in developing and testing realistic response models for use in simulation codes. As seen in previous studies, the poled ceramic from PZST undergoes anisotropic deformation during the transition from a FE to an AFE phase at -55°C. Warmer temperature tests exhibit anisotropic deformation in both the FE and AFE phase. The phase transformation is permanent at -55°C for all ceramics tests, whereas the transformation can be completely reversed at 25 and 75°C. The change in the phase transformation pressures at different temperatures were practically identical for both unpoled and poled PZST specimens. Bulk modulus for both poled and unpoled material was lowest in the FE phase, intermediate in the transition phase, and highest in the AFE phase. Additionally, bulk modulus varies with temperature in that PZST is stiffer as temperature decreases. Results from one poled-biased test for PZST and four poled-biased tests from PNZT 95/5-2Nb are presented. A bias of 1kV did not show noticeable differences in phase transformation pressure for the PZST material. However, with PNZT 95/5-2Nb phase transformation pressure increased with increasing voltage bias up to 4.5kV. 3 AcknowledgementsThe authors would like to acknowledge Thomas Pfeifle for his critical review of this report. The authors also thank Tim Scofield for overseeing fabrication of the PZST specimens.