Effects of Eu2O3 on the structure and electrical properties of 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 lead-free piezoelectric ceramics

Abstract Eu 2 O 3 (0–0.8 wt.%)-doped 0.82Bi 0.5 Na 0.5 TiO 3 –0.18Bi 0.5 K 0.5 TiO 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 2 O 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 2 O 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 2 O 3 , and the BNKT18 ceramics doped with 0.4 wt.% Eu 2 O 3 have the highest piezoelectric constant ( d 33  = 145 pC/N), highest relative dielectric constant ( e 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 2 O 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 2 O 3 .