Performance enhancement and structural defect chemistry regulation of Bi₃TiNbO₉ high-temperature piezoelectric ceramics by (W, Mn) co-doping

A novel design strategy for lead-free high-temperature piezoelectric ceramics is proposed in this study, aiming to optimize the piezoelectric performance, dielectric loss, and high-temperature stability of the Aurivillius system. By introducing (W_3/4Mn_1/4) co-dopants at the B-site, the local octahedral structure and defect chemistry of Bi₃TiNbO₉ were regulated, leading to synergistic enhancement of overall performance. The Curie temperatures of all doped samples were maintained above 900 °C. Among them, the x = 0.04 (denoted as BTNO-4WMn) composition exhibited the lowest dielectric loss (0.105) and a Curie temperature of 907.6 °C. Moreover, its d₃₃ value reached 12.7 pC/N, approximately five times that of the undoped sample, and about 93% of the initial d₃₃ was retained after annealing at 850 °C for 2 h, demonstrating excellent thermal stability. Impedance spectroscopy and activation-energy analysis further revealed a higher carrier migration barrier and more strongly suppressed high-temperature conduction in BTNO-4WMn. These results suggest that BTNO-4WMn is a promising candidate for high-temperature piezoelectric applications.