EFFECT OF OXYGEN OCTAHEDRON ROTATIONS ON THE PHASE-STABILITY, TRANSFORMATIONAL CHARACTERISTICS, AND POLARIZATION BEHAVIOR IN THE LEAD-ZIRCONATE-TITANATE CRYSTALLINE SOLUTION SERIES

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, Sawyer-Tower polarization techniques, and dilatometric measurements, The relative phase stability in the high-Zr-content end of the PZT phase diagram is believed to be directly related to the 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 octahedral 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 disordered R-type tilted state, local strains due to random octahedral rotations are believed to disrupt the long-range polar order, resulting in an inability to sustain a remnant polarization, A modified phase diagram illustrating the various oxygen octahedral tilted states and polarization behaviors is presented.