Lead-free Bi-0.5(Na0.78K0.22)(0.5)TiO3 (BNKT) piezoelectric ceramics were synthesized by the sol-gel technique. The effects of sintering temperatures on the crystal structure, microstructure, densification, dielectric, ferroelectric and electric field-induced strain behaviors of the BNKT ceramics were investigated. X-ray diffraction patterns exhibited a pure perovskite structure from 1075 to 1150 degrees C. A scanning electron microscopy study revealed an increase in grain size with increasing sintering temperature. The density of the ceramics sintered at 1150 degrees C reaches a maximum value of 5.55 g/cm(3), which is 96% of the theoretical density. BNKT ceramics sintered at an optimum temperature of 1150 degrees C exhibited a high remnant polarization of 18.5 mu C/cm(2), a high electric field-induced strain of 0.20% and dynamic piezoelectric coefficient d(33)* - (S-max/E-max) of 247 pm/V. (C) 2010 Elsevier B.V. All rights reserved.