This paper reports lead-free (Na(0.52)K(0.48-x))(Nb(0.94-x)Sb(0.06))O(3)-xLiTaO(3) compositions with significantly enhanced piezoelectric properties. The 6% Sb substituted Na(0.52)K(0.48)NbO(3) was modified by a small amount of LiTaO(3), leading to the formation of a morphotropic phase boundary between orthorhombic and tetragonal phases in the range of x = 0.035-0.04 where the materials show a strong compositional dependence of various electrical properties. Excellent properties of d(33) = 335 pC/N, k(p) = 53%, epsilon(T)(33) = 2063, Q(m) = 41 and T(c) = 291 degrees C were obtained in the composition with x = 0.04, indicating that the ceramics Studied are promising as a lead-free piezoelectric candidate. (C) 2008 Elsevier Ltd. All rights reserved.