Performance Enhancement of Piezoelectric Single Crystals Through Combination of Alternating-Current Poling and Direct-Current Poling

Alternating-current poling (ACP) is becoming a mainstream method because of its stronger ability in promoting the piezoelectric performance of ferroelectric single crystals than that of direct-current poling (DCP). A novel approach was developed by incorporating alternating-current poling and direct-current poling as modified alternating-current poling (MACP). According to the comparison of performance differences between AC-poled and DC-poled single crystals, the properties of MACP single crystals under specific conditions were systematically investigated. The improvement of single crystal performance by MACP is manifested by the multi-peak increase in piezoelectric coefficient (d33) and relative dielectric permittivity (ε33T/ε0), and the coupling factor (kt) value under higher DC bias is higher than that under DC polarization, rather than a direct superposition of DCP and ACP. Two optimal polarization windows were found: 0.2–0.25 kV/mm and 0.35–0.6 kV/mm. Compared with DCP, MACP increases the d33, ε33T/ε0 and kt, of single crystals by up to 45.67%, 21.62%, and 24.54%, respectively. This significant performance improvement, combined with its complexity, provides a new direction for customizing the performance of single crystals.