Investigation of a relationship between dielectric peak diffuseness and elastic modulus variations in a ferroelectric relaxor.

The dependence with temperature of elastic modulus of relaxor ferroelectric ceramics is modeled with a Landau-Devonshire-type cluster theory. The effective elastic modulus obtained from experimental data of ultrasonic longitudinal velocity in PCT and PLZT ferroelectric ceramics are compared with the proposed model. This comparison shows that the model is able to reproduce the dependence with temperature of elastic modulus c very well. We obtained that as impurity concentration increases in both families, the diffuseness of the transition shows important variations, but the strengths of the couplings between the polarization and the strain remain almost unchanged. In contrast, other models assigned a change in the strengths of the couplings between the polarization and the strain to explain the diffuse transition in these compounds. [ABSTRACT FROM AUTHOR]