Structure, dielectric and piezoelectric properties of (Pb_0.945Bi_0.027La_0.01)(Nb_0.95Ti_0.0625)₂O₆ piezoelectric ceramics with high Curie temperature: effect of sintering atmospheres

(Pb_0.945Bi_0.027La_0.01)(Nb_0.95Ti_0.0625)₂O₆ piezoelectric ceramic composition with high Curie temperature was synthesized via a conventional solid-state reaction method. The ceramics were sintered in the atmospheres of nitrogen (N₂) and oxygen (O₂). Effects of the sintering atmospheres on phase structure, microstructure, dielectric and piezoelectric properties of the ceramics were studied in detail. Ceramics sintered at the optimum sintering temperatures have the single orthorhombic ferroelectric phase. The atmosphere of O₂ facilitates decreasing the sintering temperatures of the ceramics. The lattice parameters of the ceramics are related to the sintering atmospheres. Microstructures of the ceramics were studied via a scanning electron microscope. The values of dielectric constant remain almost unchanged at temperatures between room temperature and about 400 °C for all ceramics. Dielectric behavior was studied via the Curie–Weiss law and modified Curie–Weiss law. Compared with the ceramics sintered in N₂, the Curie temperature of the ceramics sintered in O₂ decreases slightly to 498 °C, while the piezoelectric charge constant of the ceramics sintered in O₂ increases to 80 pC/N. For the ceramics sintered in O₂, the d ₃₃ value does not show an obvious decrease as the annealing temperature increases up to 450 °C, showing a high potential to be used in high-temperature applications as piezoelectric transducers.