High-field complex parameters characterization of PMN-PT single crystal/epoxy 1–3 composites (φ = 0.4) under a high AC electric field with a varied intensity

It is essential to characterize the high-field properties of piezoelectric composites for their applications in ultrasonic transducers. This study involved the development of an experimental characterization system of piezoelectric impedance spectra and mechanical quality factors under high-field conditions to analyze the properties of PMN-PT piezoelectric single-crystal composites. The impedance spectra and mechanical quality factors of a [0 0 1]_c-poled 0.69PMN-0.31PT single crystal/epoxy 1–3 composite disk with filling ratio φ = 0.4 under thickness resonance mode were tested at different driving voltages ranging from 1 to 120 V_pp to explore the influence of AC electric field on the material properties. By utilizing a theoretical approach, an evaluation was conducted on the variations in the material properties such as stiffness, permittivity, piezoelectric coefficient, and electromechanical coupling factor, along with respective loss factors. Our results suggest that as the AC electric field increases, the elastic modulus $c_{33}^D$ and the mechanical quality factor Q_m decrease, while the piezoelectric strain coefficient d₃₃ and the electromechanical coupling factor k_t increase. However, the dielectric coefficient ${\epsilon }_{33}^X$ does not show an obvious change in this field range. Furthermore, the elastic loss factor $\tan \varphi$, the dielectric loss factor $\tan {\delta }_{33}^{\prime }$, the piezoelectric loss factor $\tan {\theta }_{33}^{\prime }$, and the electromechanical coupling loss factor $\tan {\chi }_t$ all increase, indicating that the loss of the piezoelectric composite becomes more evident as the AC electric field grows.