Effects of BaO on the structure and electrical properties of 0.95K_0.5Na_0.5(Nb_0.94Sb_0.06)O₃-0.05LiTaO₃lead-free ceramics

Lead-free ceramics 0.95K0.5Na0.5(Nb0.94Sb0.06)O3-0.05 LiTaO3+ xmol%BaO (0 ≤ x ≤ 3.00) have been fabricated by an ordinary sintering technique. The results of x-ray diffraction show that the ceramic with a perovskite structure changes from tetragonal phase to pseudocubic phase by increasing the doping level of Ba, and the ceramics with 1.00 < x < 1.50 contain both the tetragonal and the pseudocubic phases at room temperature. After the doping with Ba, the grain growth is inhibited, the ferroelectric-paraelectric phase transition temperature (Tc) is decreased, and a diffuse phase transition is induced. The ferroelectric properties (Prand Ec) show a slight decrease with increasing x up to 1.25, and then become weakened significantly. Because of the coexistence of the tetragonal and pseudocubic phases, the piezoelectric and dielectric properties of the ceramics with 1.00 < x < 1.50 are enhanced significantly. The ceramic with x = 1.25 exhibits the optimum properties: d33= 261 pC N-1, kP= 0.52, kt= 0.46, εr= 1503, tan δ = 2.5% and Tc= 314 °C. Our results have also demonstrated that the ceramics are non-deliquescent.