Effects of lanthanum modification on rhombohedral Pb(Zr_1−xTi_x)O₃ ceramics: Part I. Transformation from normal to relaxor ferroelectric behaviors

The interruption of long-range polar order in rhombohedral ferroelectricPb(Zr_1−xTi_x)O₃ (PZT) ceramics has been systematically studied by incorporating La onto the A-site of the perovskite (ABO₃) structure for Zr/Ti ratios of 65/35 and 80/20 and various La contents. Studies have been performed by hot-stage transmission electron microscopy, dielectric spectroscopy, and Sawyer–Tower polarization (P-E) techniques. The evolution of a polar nanodomain state from a normal micron-sized domain state with increasing La content was observed. The emergence of this polar cluster state was characterized by the onset of strong frequency dispersion in the dielectric response, indicative of relaxor behavior. The La content that drives the structure into the relaxor state was found to be related to the lattice distortion of the undoped base composition.