Ultrahigh piezoelectric properties and high transparency relaxor ferroelectric single crystals obtained by the combination of rare-earth doping and AC-poling

High-performance relaxor ferroelectric single crystals, such as Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT), play a crucial role in the applications of medical ultrasonic imaging due to their high piezoelectric properties. In this study, we successfully grew a 2-in. Eu-doped PMN-PT single crystal whose composition variation and electrical properties were systematically investigated. It was found that the PT content of the crystal boule increased gradually along the growth direction, while the change of Eu³⁺ content was opposite. The property results show that Eu-doped PMN-PT single crystals exhibit a remarkable piezoelectric coefficient of 3300 pC N⁻¹ at DC-poling while maintaining the rhombohedral phase to a tetragonal phase transition temperature (T_RT) at 88 °C and the coercive field (E_C) at 2.7 kV cm⁻¹, higher to the undoped single crystals. Through the study of the local structure of Eu-PMN-PT, it illustrated that the introduction of Eu³⁺ increased the standard deviation of an A sublattice from 3.0% to 4.8%. The dopant simultaneously enhanced a tetragonal phase ratio and local structural heterogeneity, resulting in improved piezoelectric properties and temperature stability of the crystal. We further treated the doped crystals with AC-poling to obtain ultrahigh piezoelectric performance (d₃₃ > 4000 pC N⁻¹) and high transparency. This work provides a new approach to achieve a relaxor ferroelectric single crystal with high performance and transparency with good temperature stability, which could be the material of choice for optoelectronic devices in the future.