Compositional study of PLZT rainbow ceramics for piezo actuators

On-going studies have shown that the PLZT I compositional system is one which yields materials possessing some of the highest coefficients for piezoelectric and electrostrictive actuators. It has also been found that PLZT ceramics are near ideal for achieving the ultra-high displacements recently reported for the Rainbow (Reduced and INternally Biased Oxide Wafer) actuators. In order to determine the optimum composition or compositions for these Rainbow actuators, a study was conducted by preparing and processing selected formulations throughout the PLZT system. Results from this study indicate that, like the conventional direct extensional-mode materials, the maximum Rainbow bending displacements occur in materials located compositionally at the morphotropic (FE_rhomb-FE_ter) and Curie point (FE-PE, PE-AFE) phase boundaries. Examples of specific compositions for each of these regions are 2/53/47, 9/65/35 and 8.5/70/30 (La/Zr/Ti), respectively. Microstructural (grain size), electrical (dielectric constant, dissipation factor) and electromechanical (axial displacement) data are presented for selected compositions in the system