Structure and Electrical Properties of (1-x)[(K0.5Na0.5)0.95Li0.05](Nb0.95Sb0.05)O3-xSrTiO3 Lead-Free Piezoelectric Ceramics with Improved Temperature Stability

Lead-free piezoelectric ceramics (1-x)[(K0.5Na0.5)(0.95)Li-0.05](Nb0.95Sb0.05)O-3-xSrTiO(3) (abbreviated as KNLNS-xST) were sintered by the conventional method. The effects of SrTiO3 content on the structure, the electrical properties and the temperature stability of ceramics were investigated. The X-ray diffraction patterns revealed that all the ceramics have a perovskite structure, and the SEM micrographs revealed that the grain size of the ceramics was decreased with the increase of SrTiO3 content. The partial substitution of SrTiO3 decreased the Curie temperature (T-c) and shifted the orthorhombic-tetragonal phase transition temperature (TO-T) to below room temperature. It was found that the ceramics with x = 0.008 possess optimum piezoelectric properties (d(33) = 250 pC/N, k(p) = 51.7%, epsilon(r) similar to 1143 and tan delta similar to 4.45%), and the ceramics with x = 0.015 exhibit improved temperature stability, due to the shift of TO-T to below room temperature. These results indicate that these materials are promising candidates for lead-free piezoelectric ceramics for practical applications.