Piezoelectric, ferroelectric and dielectric properties of Sm2O3-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

Sm2O3 (0–0.7 wt.%)-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 (abbreviated as BNBT6) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The effects of Sm2O3 on the microstructure, dielectric properties and piezoelectric properties were investigated. X-ray diffraction (XRD) patterns show that 0.1–0.7 wt.% of Sm2O3 can diffuse into the lattice of BNBT6 ceramics forming pure perovskite phase. The SEM images indicate that the microstructure can be affected obviously by a small amount of added Sm2O3. The temperature dependence of the relative dielectric constant shows that Curie point decreases with the increase of Sm2O3. At room temperature, the ceramics doped with 0.3 wt.% Sm2O3 show quite good performance with excellent piezoelectric properties (piezoelectric constant d33 of 202 pC N−1, planar coupling factor kp of 0.30 and mechanical quality factor Qm of 101) and improved dielectric properties (relative dielectric constant ɛr of 2018 and dissipation factor tan δ of 0.056). Moreover, all BNBT6 − x (wt.%) Sm2O3 ceramics exhibit a typical relaxor behavior with diffuse phase transition characteristics and the degree of ferroelectric relaxation behavior is enhanced with the increase of Sm2O3 content.