Crystal structure and properties of K0.5Na0.5NbO3-Bi0.5Na0.5TiO3-LiSbO3 lead-free piezoelectric ceramics

(1 - x)(0.99K(0.5)Na(0.5)NbO(3)-0.01Bi(0.5)Na(0.5)TiO(3))-xLiSbO(3) (KNN-BNT-LS100x, x = 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.1) lead-free piezoelectric ceramics were fabricated by conventional ceramic technique. The crystal structure, dielectric and piezoelectric properties of the ceramics were investigated. The X-ray diffraction (XRD) analysis revealed that the ceramics sintered in air at 1040-1080 degrees C for 3-4 h possessed a pure perovskite structure when LiSbO3 content was 0-5 mol%. A morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases was identified in the composition range of 0.01 < x < 0.04. The Curie temperature (T,) and the orthorhombic-tetragonal transition temperature (TO-T) shifted to lower temperature with increasing LiSbO3 content. The ceramics close to the MPB exhibited enhanced dielectric and piezoelectric properties. The highest piezoelectric constant d(33) = 250 pC/N, electromechanical coupling factors, k(p) = 0.29, k(t) = 0.35 and k(33) = 0.447, mechanical quality factor, Q(m) =33, T-c =339 degrees C, TO-T = 65 degrees C, dielectric constant, epsilon(T)(33)/epsilon(0) = 640 and loss tangent, tan delta = 0.031 were obtained for the KNN-BNT-LS4 ceramic which has a tetragonal phase near the MPB. (C) 2010 Elsevier B.V. All rights reserved.