Top-seeded solution growth and characterization of rhombohedral PMN-30PT piezoelectric single crystals

Piezoelectric single crystals from 70Pb(Mg_1/3Nb_2/3)O₃-30PbTiO₃ solid solution were grown by a top-seeded solution growth method that prevented phase segregation and promoted (0 0 1) growth. Rhombohedral symmetry was confirmed by polarized light microscopy and the dielectric, piezo- and ferro-electric properties were characterized. A dispersive maximum of dielectric permittivity appears around T_C = 125 °C, which slightly shifts towards higher temperatures with increasing frequency, indicating weak relaxor behaviour. Rhombohedral-tetragonal phase transition was detected at 105 °C. This temperature is higher than the depoling temperature of the morphotropic phase boundary compositions (50-80 °C), thus extending the upper limit of the application temperature for electromechanical transducers. The piezoelectric coefficient (d₃₃) was found to be 1240 pC N^-1, with a strain level reaching 0.12% at an electric field of 12 kV cm^-1. The longitudinal electromechanical coupling factor k₃₃ reaches 85%, which persists upon heating up to 100 °C.