Piezoelectric, ferroelectric and dielectric properties of Sm 2O 3-doped (Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 lead-free ceramics

Abstract

Sm 2O 3 (0–0.7 wt.%)-doped (Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 (abbreviated as BNBT6) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The effects of Sm 2O 3 on the microstructure, dielectric properties and piezoelectric properties were investigated. X-ray diffraction (XRD) patterns show that 0.1–0.7 wt.% of Sm 2O 3 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 Sm 2O 3. The temperature dependence of the relative dielectric constant shows that Curie point decreases with the increase of Sm 2O 3. At room temperature, the ceramics doped with 0.3 wt.% Sm 2O 3 show quite good performance with excellent piezoelectric properties (piezoelectric constant d 33 of 202 pC N −1, planar coupling factor k p of 0.30 and mechanical quality factor Q m of 101) and improved dielectric properties (relative dielectric constant ɛ r of 2018 and dissipation factor tan δ of 0.056). Moreover, all BNBT6 − x (wt.%) Sm 2O 3 ceramics exhibit a typical relaxor behavior with diffuse phase transition characteristics and the degree of ferroelectric relaxation behavior is enhanced with the increase of Sm 2O 3 content.