Phase Transition and High Piezoactivity of Sr Doped Lead-Free (Na_0.53K_0.422Li_0.048)(Nb_0.89Sb_0.06Ta_0.05)O₃ Ceramics

Lead-free piezoelectric ceramics ((Na_0.53K_0.422Li_0.048)(Nb_0.89Sb_0.06Ta_0.05)O₃ (NKLNST) + x mol SrCO₃ are prepared by conventional solid state sintering method. The specimens with pure perovskite structure show tetragonal phase at x≤0.01, and become pseudo-cubic phase at x≥0.02. A lattice parameter discontinuity is found in the specimens with 0.004≤x≤0.0075, along with a great improvement in piezoactivity. The 0.004mol SrCO₃ added NKLNST ceramics possesses outstanding performances of k_p=0.53, k_t =0.26, and d₃₃=309pC/N. Moreover, the Sr²⁺ modification inhibits the grain growth, decreases the Curie temperature, and induces a diffuse phase transition.