High-temperature piezoelectric properties and thermal stability of BF-BT-based ceramics by double A-site ion modification

This paper investigates 0.69BiFeO(3)-0.31BaTiO(3)+x(0.8Bi(0.5)Na(0.5)TiO(3)-0.2Bi(0.5)K(0.5)TiO(3)) (abbreviated as 0.69BF-0.31BT+x(0.8BNT-0.2BKT) (0 <= x <= 0.025) quaternary high-temperature lead-free piezoelectric ceramics. X-ray diffraction(XRD) analysis reveals that these ceramics exhibit morphotropic phase boundaries (MPB) with coexistence of rhombohedral (R) and pseudo-cubic (Pc) phases. The in-situ d(33) measurements indicate that 0.69BF-0.31BT+x(0.8BNT-0.2BKT) possesses excellent thermal stability, achieving an in-situ d(33) of 687 pC/N at T-dr = 382 degrees C, and a high Curie temperature (T-c = 474 degrees C). Transmission electron microscopy (TEM) results show that the high depolarization temperature (T-dr) and excellent piezoelectric properties are attributed to compositional inhomogeneity introduced by the incorporation of double relaxation ferroelectrics (0.8BNT-0.2BKT), resulting in the formation of polar nanoregions (PNRs). This design demonstrates that the quaternary system of BF-BT+(BNT-BKT)-based ceramics serves as a promising example for optimizing high-temperature lead-free piezoelectric ceramics.