Enhancement of piezoelectric properties in PMN-PT single crystal-based 2–2 composites via alternating current polarization

This study systematically investigates the enhancement of piezoelectric properties in PMN-PT single crystal-based 2–2 composites via alternating current polarization (ACP). The composites were fabricated using the conventional dice-and-fill method, and the effects of key ACP parameters—electric field strength (E_p), frequency (f), and cycle number (C) were evaluated. Under the optimal ACP conditions (E_p = 1 kV/mm, f = 1 Hz, C = 15), the material exhibited a free dielectric constant (ε33T[jls-end-space/]/ε0[jls-end-space/]), electromechanical coupling factor (kt), and piezoelectric coefficient (d₃₃) of 7879, 0.68, and 2185 pC/N, respectively. These values represent significant improvements of 18.80%, 14.03%, and 7.91% compared to those achieved by direct current polarization (DCP). To elucidate the underlying mechanism, piezoresponse force microscopy (PFM) was employed. The analysis revealed that the performance enhancement originates from a high-density domain wall structure induced by ACP, which refines the average domain size from 1.08 μm (DCP) to 0.82 μm (ACP). This refined domain configuration effectively facilitates ferroelectric domain switching and enhances the extrinsic contribution to the piezoelectric response. Therefore, ACP technology, characterized by its high efficiency and short processing cycle, presents a promising strategy for achieving performance breakthroughs in linear array ultrasonic transducers for applications in medical imaging and non-destructive testing.