Effect of sintering temperature on 0.75BiFeO3-0.25BaTiO3 of lead free high temperature piezoelectric ceramics

0.75BiFeO(3)-0.25BaTiO(3) (75BF-25BT) has been widely concerned because of its lead-free and high Curie temperature. However, the phenomenon of Bi2O3 volatilization and Fe3+ valence change in the sintering process of BF-BT ceramics leads to higher defect ion concentration and dielectric loss tan delta. In order to make it have higher potential in low cost, environmental protection and high temperature piezoelectric applications, researchers used different methods to study 75BF-25BT. In this paper, the excellent performance of 75BF-25BT was studied by changing the sintering temperature. Lead free piezoelectric ceramic powders were prepared by traditional solid-state reaction method. After pressing, the samples were sintered at different temperatures (960 degrees C, 980 degrees C, 1000 degrees C, 1020 degrees C, 1040 degrees C). XRD analysis shows that all ceramic samples are perovskite structure, and there is no impurity phase. The lattice constant of ceramic samples at different sintering temperatures first increases and then decreases, and reaches the maximum at 1020 degrees C. At the same time, the relative density of ceramic samples is higher than 94 %, with the highest value of 95.1 % at 1020 degrees C. Compared with 960 degrees C, the remnant polarization value Pr is obviously increased, and the highest value is 15.4 C/cm(2) at 1020 degrees C. The Curie temperature is inversely correlated with the sintering temperature. With the increase of sintering temperature, the Curie temperature decreases. The highest piezoelectric constant d(33), dielectric constant epsilon(r), lowest dielectric loss tan delta and Curie temperature T-c are 111 pC/N, 388, 2.3 % and 554 degrees C respectively at 1020 degrees C due to the influence of large lattice constant, high relative density and large remnant polarization value. These results show that the optimum sintering temperature is 1020 degrees C, Bi3+ volatilization is less, defect ion concentration is reduced, and it has excellent electrical properties.