Effect of La_2O_3 on the microstructure and electrical properties of 0.82Bi_(0.5)Na_(0.5)TiO_3-0.18Bi_(0.5)K_(0.5)TiO_3 ceramics

摘要

La_2O_3-doped lead-free 0.82Bi_(0.5)Na_(0.5)TiO_3-0.18Bi_(0.5)K_(0.5)TiO_3 (abbreviated to 0.82BNT-0.18BKT) piezoelectric ceramics were synthesized by the conventional mixed-oxide method, and the effect of La_2O_3 addition on the dielectric and piezoelectric properties was investigated. X-ray diffraction (XRD) patterns show that La_2O_3 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 grain size of the 0.82BNT-0.18BKT ceramics increased with the addition of La_2O_3 doping. The electrical properties of 0.82BNT-0.18BKT ceramics have been greatly improved by certain amount of La_2O_3 substitutions. At room temperature, the 0.82BNT-0.18BKT ceramics doped with 0.25 wt. % La_2O_3 exhibited the optimum properties with high piezoelectric constant (d_(33) = 142 pC/N) and high planar coupling factor (k_p = 0.23).