Effects of Fe₂O₃ doping on the electrical properties of Na_0.47Bi_0.47Ba_0.06TiO₃ lead-free ceramics

The Na_0.47Bi_0.47Ba_0.06Ti_1-xFe_xO_3-Δ lead-free piezoelectric ceramics (BNBT-100xFe, x = 0, 0.01, 0.02, 0.03) were synthesized by using the solid-state reaction technique. X-ray powder diffraction patterns demonstrate that the doping Fe₂O₃ has totally diffused into the crystal lattice of the ceramics and form a pure perovskite structure. Enhanced piezoelectric property is obtained at x = 0.01, which is reflected on the enhanced remnant polarization (P_r) and a giant piezoelectric constant (d₃₃) up to 168 pC/N. The increasing ferroelectric-to-relaxor phase transition temperature (T_F-R) on dielectric permittivity curves suggest the enhanced ferroelectric characteristics with increasing the Fe³⁺ content. By using the complex ac impedance analysis, the grain, grain boundary and electrode effects are all detected at the appreciate composition. The resistivity behavior of the samples is sensitive to the doping Fe³⁺ concentration, and additionally, the oxygen vacancies play an important role in this characteristic.