Structural and property studies of high Zr-content lead zirconate titanate

Lead zirconate titanate (PZT) ceramics with Zr/Ti ratios between 95/5 and 55/45 have been examined by transmission electron microscopy (TEM), dielectric spectroscopy, and Sawyer-Tower polarization measurements. It is believed that in the high Zr-content end of PZT phase diagram, that the relative phase stability is directly related to a coupling of the polarization to various oxygen octahedral rotational systems. The transformation between the high and low temperature rhombohedral ferroelectric phases (FE(R(HT))-FE(R(LT))) in PZT 90/10 was found to be associated with a transition between a high temperature M-type and a low temperature R-type oxygen rotational system. However, with increasing Ti-content (Zr/Ti < 80/20) a transition between a disordered R-type tilted state to a low temperature ordered R-type tilted state was found near the FE(R(HT))-FE(R(LT)) boundary. The transition between the disordered and ordered R-type tilted states became increasingly gradual with increased Ti-content. In the FE(R(LT)) state, local strains due to random octahedral rotations are believed to disrupt the long-range polar order, resulting in metastability effects characterized by dielectric relaxation.