Piezoelectric, ferroelectric and dielectric properties of La_2O_3-doped (Bi_(0.5)Na_(0.5))_(0.94)Ba_(0.06)TiO_3 lead-free ceramics

摘要

La_2O_3 (0-0.8 wt.%)-doped (Bi_(0.5)Na_(0.5))_(0.94)Ba_(0.06)TiO_3 (abbreviated as BNBT6) lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction. The influences of La_2O_3 on the microstructure, the dielectric, ferroelectric and piezoelectric properties of the composites were investigated. X-ray diffraction (XRD) patterns indicate that 0.2-0.8 wt.% of La_2O_3 has diffused into the lattice of BNBT6 ceramics. Consequently, a pure perovskite phase is formed. SEM images show that the microstructure of the ceramics is changed with the addition of a small amount of La_2O_3. The temperature dependence of the relative dielectric constant shows that Curie point decreases with the increase of La_2O_3. At room temperature, the ceramics doped with 0.6 wt.% La_2O_3 show superior performance with high piezoelectric constant (d_(33) = 167 pC/N), high planar electromechanical coupling factor (k_p = 0.30), high mechanical quality factor (Q_m =118), high relative dielectric constant (ε_rt = 1470) and lower dissipation factor (tanδ = 0.056) at a frequency of 10 kHz.