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

Abstract

0.75BiFeO3-0.25BaTiO3 (75BF-25BT) has been widely concerned because of its lead-free and high Curie temperature. However, the phenomenon of Bi2O3 volatilization and Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> valence change in the sintering process of BF-BT ceramics leads to higher defect ion concentration and dielectric loss tanδ. In order to make it have higher potential in low cost, environmental protection and high temperature piezoelectric applications, researchers used different methods to study 75BF25BT. 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 °C, 980 °C, 1000 °C, 1020 °C, 1040 °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 °C. At the same time, the relative density of ceramic samples is higher than 94 %, with the highest value of 95.1 % at 1020 °C. Compared with 960 °C, the remnant polarization value Pr is obviously increased, and the highest value is 15.4 C/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 1020 °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 d33, dielectric constant εr, lowest dielectric loss tanδ and Curie temperature Tc are 111 pC/N, 388, 2.3 % and 554 °C respectively at 1020 °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 °C, Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> volatilization is less, defect ion concentration is reduced, and it has excellent electrical properties.