Effects of BaO on the structure and electrical properties of 0.95K0.5Na0.5(Nb0.94Sb0.06)O3–0.05LiTaO3lead-free ceramics

Lead-free ceramics 0.95K 0.5 Na 0.5 (Nb 0.94 Sb 0.06 )O 3 –0.05 LiTaO 3 + x mol%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 ( T c ) is decreased, and a diffuse phase transition is induced. The ferroelectric properties ( P r and E c ) 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: d 33 = 261 pC N −1 , k P = 0.52, k t = 0.46, ε r = 1503, tan δ = 2.5% and T c = 314 °C. Our results have also demonstrated that the ceramics are non-deliquescent.