Dielectric and piezoelectric properties are presented for lead-free piezoelectric compositions in the Na0.5K0.5NbO3-LiTaO3-BiScO3 ternary system, focusing on the compositional join 0.98[(1 - x)(Na0.5K0.5NbO3)-xLiTaO(3)]-0.02[BiScO3]; 0 <= x <= 0.1. The end-member composition, 0.98Na(0.5)K(0.5)NbO(3)-0.02BiScO(3) has previously been reported to exhibit relatively high piezoelectric coefficients; the present paper examines changes in properties resulting from incorporation of LiTaO3. Measurements of relative permittivity versus temperature showed a Curie peak at similar to 350 degrees C in x <= 0.02 samples. This peak broadened as the LiTaO3 content increased from x=0.02 to 0.03. At x=0.05 and 0.07, the relative permittivity-temperature curve became even more diffuse, and a second peak occurred at similar to 470 degrees C; transmission electron microscopy revealed this was the result of elemental segregation and the formation of a core-shell grain structure. Maximum values of d(33) piezoelectric charge coefficients were similar to 200 pC/N in samples x=0.01 and 0.02, for which dielectric and X-ray diffraction data inferred an orthorhombic-tetragonal phase transition close to room-temperature. (C) 2011 Elsevier B.V. All rights reserved.