Piezoelectric and dielectric properties of Sm2O3-doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 ceramics

Sm2O3 (0–0.7 wt.%)-doped lead-free 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 (abbreviated to 0.82BNT–0.18BKT) piezoelectric ceramics were synthesized by the conventional mixed-oxide method, and the effect of Sm2O3 addition on the dielectric and piezoelectric properties was investigated. X-ray diffraction (XRD) patterns show that Sm2O3 diffuses into the lattice of the 0.82BNT–0.18BKT ceramics to form a solid solution with a pure perovskite structure. SEM images indicate that the microstructure become uniform by doping a small amount of Sm2O3. The electrical properties of 0.82BNT–0.18BKT ceramics have been greatly improved by certain amount of Sm2O3 substitutions. At room temperature, the 0.82BNT–0.18BKT ceramics doped with 0.3 wt.% Sm2O3 exhibited the optimum properties with high piezoelectric constant (d33 = 147 pC/N) and high planar coupling factor (kp = 22.4%).