Improved dielectric and piezoelectric thermal stability by chemical homogenization in CuO-modified 0.75BiFeO3-0.25BaTiO3 piezoceramics

0.75BiFeO 3 -0.25BaTiO 3 lead-free ceramics have been considered promising candidates for high-temperature piezoelectric applications. However, their dielectric and piezoelectric properties severely degrade with increasing temperature. In this work, improved dielectric and piezoelectric thermal stability was obtained in CuO-modified 0.75BiFeO 3 -0.25BaTiO 3 ceramics. CuO addition increases the volume fraction of the rhombohedral phase in the 0.75BiFeO 3 - 0.25BaTiO 3 ceramics and makes the chemical heterogeneity disappear. The dielectric and piezoelectric anomalies are eliminated near 300 °C and return with CuO additions, and the temperature degradations of the dielectric constant and piezoelectric coefficient of 0.75BiFeO 3 -0.25BaTiO 3 ceramics with 0.008 mol CuO in the range from 25 to 400 °C decrease by 85% and 60%, respectively. Furthermore, the depoling temperature and piezoelectric coefficient of 0.75BiFeO 3 -0.25BaTiO 3 ceramics with 0.008 mol CuO are 570 °C and 131 pC/N, respectively. These results indicate that CuO addition is an effective approach to improve both the dielectric and piezoelectric thermal stability of 0.75BiFeO 3 -0.25BaTiO 3 ceramics.