Integrated piezoelectric structures under external mechanical stress: Theory and experiments

The purpose of the study is to understand and predict the behavior of integrated structures when submitted to external or internal mechanical stress. This is of primary importance in the field of thick or thin film technology. In our laboratory, a modified KLM model that enables to compute the electroacoustic behavior of piezoelectric materials under external mechanical stress has been developed. In this present work, we produce the first experimental results of electromechanical characterizations of reference materials under external mechanical stress in order to further validate our model. A static stress (with a stepper motor) and a superimposed dynamic wave (with PZT actuator) are applied to PZT type materials (PZ21 and PZ26). The hysteretic behavior and the evolution with the stress (0 to 100 MPa) of plane wave velocity are presented for the two samples. The evolution of ultrasonic wave velocities along the direction of stress are treated using conventional pulse echo technique. Results validate the acoustical and mechanical method but show high sensitivity of the mechanical aspect and reveal the need to enhance the experimental setup to obtain more accurate values.