Lanthanum Dependence of Elastic and Piezoelectric Properties of PLZT Ceramics with a Zr/Ti Ratio of 65/35

Abstract
The elastic and piezoelectric properties of PLZT ceramics with a 65/35 Zr/Ti ratio undergo pronounced changes as La is added to the structure. At the rhombohedral‐tetragonal phase boundary, material constants plotted as functions of La concentration show strong discontinuities in slope; these discontinuities provide a precise means of locating the boundary. The radial‐mode coupling factor, kp, compliance coefficient, S11E, and piezoelectric coefficient, d31, attain peak values at the boundary, whereas Poisson's ratio, σE, and the resonance‐frequency constant exhibit pronounced minima. This behavior is evidence of the increasing ferroelastic sensitivity of the material as the distortion angle of the rhombohedral phase approaches a minimum.