Electrostriction measurements in diffuse phase transition materials and perovskite glass ceramics

Materials with diffuse phase transitions are of much interest for applications in very smart systems. The main advantage they have over conventional materials is the tunable nature of their nonlinear properties such as electrostriction. Electrostriction is the fundamental mechanism of electromechanical coupling in these and all insulating materials, and is of interest for sensor, actuator, and tunable transducer applications. Electrostriction measurements are also of interest in trying to better understand the nature of the diffuse transition. In this study, a group of ferroics (Ca/PMN-PT, La/PMN-PT, PLZT, BTS, and BST) with diffuse transitions were tested using the first converse effect. This technique involves measuring the stress dependence of the dielectric stiffness β_ij to obtain electrostrictive tensor coefficients. This method has been previously verified by measuring separated Q_ijkl coefficients for low-K dielectrics. Q₃₃ coefficients of the order of 10^-3 m⁴/C² were obtained for the ferroics. A figure of merit is proposed for evaluating these ferroics in sensor applications, based on their fractional change in capacitance under applied stress. A preliminary correlation of the electrostriction effects with the diffuseness of the phase transition (DPT) is also done. A family of perovskite glass ceramics with different modifiers that had been subjected to different ceramming temperatures was also investigated and found to have promising sensor applications. The electrostrictive and dielectric properties were found to vary with the heat treatment