Lead-free 0.995K(0.48)Na(0.48)Li(0.04)Nb((1-x))SbxO3-0.005BiAlO(3) piezoelectric ceramics with perovskite structure were designed and prepared with conventional ceramic fabrication techniques. The phase transitions of the ceramics were determined by X-ray diffraction patterns and the temperature dependence of dielectric properties. The ceramics possessed an orthorhombic tetragonal phase boundary with x = 0 and exhibited the coexistence of rhombohedral orthorhombic and orthorhombic tetragonal phase boundaries at around room temperature, with 0.02 <= x <= 0.03. Upon further increasing the Sb content, the crystal structure transformed to the rhombohedral-tetragonal phase coexistence in the composition range of 0.04 <= x <= 0.05. Next, the phase structure turned to a sole rhombohedral symmetry with x >= 0.06. A clearly enhanced piezoelectric activity was demonstrated for the ceramic with the rhombohedral-tetragonal phase boundary composition x = 0.05, where the values of piezoelectric constant d(33), planar and thickness electromechanical coupling coefficients reached 205 pC/N, 0.360 and 0.437, respectively. (C) 2016 Elsevier Ltd. All rights reserved.