Nonlinear stress-strain behavior of piezoelectric ceramics under tensile loading

Fracture strength and stress-strain behavior under tensile stress in piezoelectric ceramics have been investigated with special emphasis on the effect of environmental temperature. The materials used in this work are the commercial piezoelectric ceramics, PbZrO₃-PbTiO ₃ (PZT) and PLZT. An attempt was first made to evaluate the tensile strength properties at the room temperature of PZT samples having a specially designed specimen geometry. Not only fracture strength, but also elastic properties, tensile modulus and Poisson´s ratio, were evaluated and then the stress-strain behavior under tension was investigated. As a result, stress-strain response under tension for piezoelectric ceramics, PZT and PLZT, was confirmed to be nonlinear. The nonlinearity in the stress-strain relationship under compression loading has already been reported by some investigations. However, very little work has been done on the tensile stress-strain relationship, as studied in this paper. The results of tensile test for PZT samples at the various environmental temperatures indicated that the stress-strain response of poled and nonpoled samples was nonlinear independent of test temperature. The strength of both the poled samples and the nonpoled samples increased linearly against test temperature. Moreover, acoustic emission monitoring was performed simultaneously during tensile tests, and thus the tensile failure process in piezoelectric ceramics was discussed. It was also pointed out that the tensile strength of PLZT increased monotonically against the amount of La