Effects of Eu 2O 3 on the structure and electrical properties of 0.82Bi 0.5Na 0.5TiO 3–0.18Bi 0.5K 0.5TiO 3 lead-free piezoelectric ceramics

Abstract

Eu 2O 3 (0–0.8 wt.%)-doped 0.82Bi 0.5Na 0.5TiO 3–0.18Bi 0.5K 0.5TiO 3 (BNKT18) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The compositional dependence of phase structure and electrical properties of the BNKT18 ceramics was studied. X-ray diffraction (XRD) data shows that 0.2–0.8 wt.% Eu 2O 3 has diffused into the lattice of BNKT18 ceramics and forms a pure perovskite phase. SEM images indicate that the grain size of BNKT18 ceramics decreases with the increase of Eu 2O 3 content, and all the modified ceramics have a clear grain boundary and a uniformly distributed grain size. At room temperature, the ferroelectric and piezoelectric properties of the BNKT18 ceramics have been improved with the addition of Eu 2O 3, and the BNKT18 ceramics doped with 0.4 wt.% Eu 2O 3 have the highest piezoelectric constant ( d 33 = 145 pC/N), highest relative dielectric constant ( ε r = 1134) and lower dissipation factor (tan δ = 0.045) at a frequency of 10 kHz. The BNKT18 ceramics doped with 0.2 wt.% Eu 2O 3 have the highest planar coupling factor ( k p = 0.251). The temperature dependence of the relative dielectric constant shows T m increases with the addition of Eu 2O 3.