Abstract: (K_0.45Na_0.55)_0.98Li_0.02(Nb_0.77Ta_0.18Sb_0.05)O₃-xBaZrO₃ (NKNLST-xBZ, x = 0–0.020 mol) lead-free piezoelectric ceramics were prepared by solid state reaction method. The effect of BaZrO₃ doping amount on the piezoelectric, dielectric, electromechanical and ferroelectric properties were investigated systematically. The results revealed that the crystal structures transformed from orthorhombic phase to tetragonal phase with BaZrO₃ doping amount increasing, and the coexistence of orthorhombic-tetragonal phases were observed in the x range from 0.005 to 0.008. Under the condition of two phases co-existence, the ceramic grain became small and uniform and dielectric loss tanδ significantly decreased, while the piezoelectric constant d₃₃ and planar electro-mechanical coupling factor kp increased. The dielectric constant ε^T₃₃ /ε₀ of this system ceramics increased continuously with the increase of the BaZrO₃ doping amount and the phase transition temperatures shifted to lower temperature. The optimized piezoelectric properties could be obtained at the x = 0.005 composition ceramic as follows: the piezoelectric constant d₃₃ = 372 pC/N, planar electromechanical coupling coefficient k_p = 47.2%, dielectric loss tanδ = 3.1%, a high dielectric constant ε^T₃₃ /ε₀ = 1470 and Curie temperature T_c=208℃.

Key words: sodium potassium niobate, barium zirconate, lead-free piezoelectric ceramics, perovskite