Enhancing response and thermal stability of PYN–PHT ceramics through design of “mixed-state” domain structures

Piezoceramics have long encountered difficulties in simultaneously attaining a high Curie temperature (T_C) and extraordinary electrical characteristics due to the issue of thermal depolarization. To handle this, a novel 0.1 Pb(Yb_0.5Nb_0.5)O₃ (PYN)–0.9 Pb(Hf_1−xTi_x)O₃ (PHT) + x mol%Ta₂O₅ piezoelectric ceramic was prepared using solid-state sintering method. We developed a synergistic strategy in introducing local heterogeneity into the tetragonal phase, where doping with heterovalent Ta⁵⁺ ions significantly reduces the temperature dependence of PYN–PHT piezoelectric ceramics. The structure and electrical behavior of obtained ceramics were methodically investigated using various analytical approaches. Our innovative composition, PYN–PHT–0.6Ta, showcases tetragonal phases. It exhibits impressive results, such as a piezoelectric coefficient d₃₃ of 560 pC/N, an electromechanical coupling coefficient of 0.7 and a T_C of 312.2 °C. Doping with Ta⁵⁺ ions unveils the formation of small size, mixed-state domain structure in enhancing piezoelectric and dielectric properties of ceramics. Additionally, the pinning effect of tetragonal phase contribute to the remarkable temperature stability (the variation in d₃₃ is only 6.03 % from 25 °C to 300 °C) of the material. Overall, the exceptional performance and high quality of PYN–PHT–xTa ceramics hold great promise for high-temperature application in future microdevices.