Effect of Oxygen Octahedron Rotations on the Phase Stability, Transformational Characteristics, and Polarization Behavior in the Lead Zirconate Titanate Crystalline Solution Series

Abstract

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.