Lead-free (K0.5Na0.5)(Nb0.7Ta0.3)O-3 (KNNT) piezoelectric thin films were prepared on Pt(111)/TiO2/SiO2/Si(100) substrates by chemical solution deposition method. The effects of annealing temperatures 550, 600, 650, 700, and 750 degrees C on microstructure, leakage current, ferroelectric, and piezoelectric properties of the KNNT thin films were investigated. The largest remanent polarization P-r (10.5 mu C/cm(2)), piezoelectric coefficient d(33) (62 pm/V), and lowest leakage current density (4.6 x 10(-6) A/cm(2) under 120 kV/cm) of the KNNT film were obtained with annealing at 700 degrees C. The mechanisms concerning the enhancement in d(33) are discussed, and the improved piezoelectric performance of the KNNT film suggests a promising candidate for piezoelectric thin film devices. (C) 2011 Elsevier B.V. All rights reserved.