Piezoelectric properties and time stability of lead-free (Na0.52K0.44Li0.04)Nb1−x−ySbxTayO3 ceramics

(Na0.52K0.44Li0.04)Nb1−x−ySbxTayO3 (NKLNST-x/y) lead-free piezoelectric ceramics were prepared by conventional solid-state reaction method. Their crystal structure was determined by X-ray diffraction, and the temperature dependence of dielectric constants was measured. It is found that Sb5+ and Ta5+ diffuse into the (Na0.52K0.44Li0.04)NbO3 lattice to form a solid solution with a perovskite structure. The co-substitution of Sb5+ and Ta5+ for B-site Nb5+ decreases both the paraelectric cubic-tetragonal phase transition temperature (TC) and the tetragonal-orthorhombic phase transition temperature (TO-T) of the (Na0.52K0.44Li0.04)NbO3 ceramics, and results in significant improvements in piezoelectric properties. Enhanced electrical and electromechanical responses of d33=335 pC/N and kp=0.46 are obtained in the ceramics with x/y=0.08/0.05. Meanwhile, piezoelectric properties of the NKLNST-0.08/0.05 ceramic show no obvious reduction and dielectric loss increases slightly when exposed in air for 30 day. The results indicate that NKLNST-x/y ceramic is a promising lead-free piezoelectric candidate material.