The effect of machining-generated residual stress on the properties of single crystal piezoelectric layers in high-frequency ultrasonic transducers†

Abstract

During the mechanical thinning process for preparing ultrathin (approximately 100 μm) piezoelectric single crystals (SC) for high-frequency ultrasonic transducers, a significant degradation in performance has been observed in Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PMN–PT) SC sheets. Experimental results indicate that this degradation is primarily due to machining-generated residual stress during the thinning process. Upon the removal of mechanical force, residual stress is induced within the PIN–PMN–PT SC sheet, leading to a decline in the dielectric, piezoelectric, and electromechanical properties. The residual stress significantly impacts both external surface roughness and internal domain structure of the SC sheet, directly affecting its electrical performance. Additionally, the residual stress exacerbates electrical fatigue in the PIN–PMN–PT SC sheet during practical use. To address these issues, high-temperature annealing following mechanical thinning has been demonstrated to effectively eliminate or minimize residual stress, thereby substantially mitigating its adverse effects. This process enhances the electrical properties, thermal stability, and resistance to electrical fatigue of the SC sheet. This study offers insights into optimizing the performance optimization of high-performance SC sheets for improving the performance of high-frequency transducers.