Improved piezoelectric properties of 2–2 piezoelectric single crystal composites for acoustic transducer applications via alternating current polarization

•ACP was used to improve the properties of 2–2 PSCCs for the first time.•Improvement of d33 of 36% was achieved in ACP samples.•A high d33 of 1700 pC/N was obtained, surpassing reported piezocomposites. Piezoelectric single-crystal composites with 2–2 type (2–2 PSCCs) have attracted widespread attention in acoustic transducer applications due to the higher hydroacoustic piezoelectricity and electromechanical coupling performance compared to traditional ceramic piezoelectric composites. At present, alternating current polarization (ACP) has been proven as an effective method to improve the performance of piezoelectric materials. Here, to optimize the conditions of ACP, the influence of ACP on the properties of 2–2 PSCCs with different amplitudes, frequencies, and polarization cycles of the electric field was investigated. Compared to direct current polarized (DCP) samples, the piezoelectric coefficient (d33), the relative free dielectric permittivity (ε33T/ε0), and the thickness electromechanical coupling factor (kt) of ACP samples were improved by 36%, 60%, and 3.5% respectively. Furtherly, the domain structure of DCP and ACP samples was compared, and the result demonstrates that the improvement in piezoelectric and dielectric properties is related to the grown domain size in single crystals. This work shows a simple and effective method to improve the performance of 2–2 PSCCs.