Preparation and characterization of Pb(Lu_1/2Nb_1/2)O₃–Pb(In_1/2Nb_1/2)O₃–PbTiO₃ ternary ferroelectric ceramics with high phase transition temperatures

To explore new relaxor-PbTiO₃ systems for high-power and high-temperature electromechanical applications, a ternary ferroelectric ceramic system of Pb(Lu_1/2Nb_1/2)O₃–Pb(In_1/2Nb_1/2)O₃–PbTiO₃ (PLN–PIN–PT) have been investigated. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the as-prepared PLN–PIN–PT ceramics near the morphotropic phase boundary (MPB) were characterized. A high rhombohedral-tetragonal phase transition temperature T_R-T of 165°C and a high Curie temperature T_C of 345°C, together with a good piezoelectric coefficient d₃₃ of 420 pC/N, were obtained in 0.38PLN–0.20PIN–0.42PT ceramics. Furthermore, for (0.8−x)PLN–0.2PIN–xPT ceramics, the temperature-dependent piezoelectric coefficients, coercive fields and electric-field-induced strains were further studied. At 175°C, their coercive fields were found to be above 9.5 kV/cm, which is higher than that of PMN–PT and soft P5H ceramics at room temperature, indicating PLN–PIN–PT ceramics to be one of the promising candidates in piezoelectric applications under high-driven fields. The results presented here could benefit the development of relaxor-PbTiO₃ with enhanced phase transition temperatures and coercive fields.