Effects of Li content on the phase structure and electrical properties of lead-free (K0.46−x∕2Na0.54−x∕2Lix)(Nb0.76Ta0.20Sb0.04)O3 ceramics

Lead-free (K0.46−x∕2Na0.54−x∕2Lix)(Nb0.76Ta0.20Sb0.04)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=259pC∕N, 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.