Effects of Li content on the phase structure and electrical properties of lead-free (K_0.46-x/2 Na_0.54-x/2Li_x) (Nb _0.76Ta_0.20Sb_0.04)O₃ ceramics

Lead-free (K0.46-x2 Na0.54-x2 Lix) (Nb0.76 Ta0.20 Sb0.04) O3 piezoelectric ceramics were prepared by the conventional solid state sintering method without cold-isostatic pressing process. The x-ray diffraction and Raman scattering results show that the phase structure of the ceramics undergoes a transition from pseudocubic to tetragonal phase with increasing x from 0 to 0.10. Significantly enhanced electrical properties (d33 =259 pCN, kp =0.42, εr =1653, and tan δ=0.027) were obtained in the ceramics with x=0.04 near the morphotropic phase boundary, and only the tetragonal-cubic phase transition was observed above the room temperature in the εr -T curve. The temperature stability of the ceramics with x=0.04 was also investigated.