Thin (Na,K)NbOx perovskite films (NKN) have been deposited on SiO2/Si(0 0 1) substrates at low temperatures, from 350degreesC to 550degreesC, by RF magnetron sputtering. The effects of substrate temperature on microstructure, electrical-, and mechanical properties of the NKN films have been studied. X-ray diffraction analysis revealed that films deposited at temperatures in the range of 450-550degreesC were crystalline, growing as a single phase, with a preferred orientation of (0 0 1). Films deposited at 350degreesC, were shown to be amorphous. The growth temperature had a strong influence on the electrical properties of the NKN films and the relative dielectric constants of the obtained films were in between 38 and 78. Variations of the mechanical properties of the NKN films were observed for different substrate temperatures: The elastic moduli and the hardness values ranged from 205 +/- 26 to 93 +/- 29 GPa, and from 12 +/- 2 to around 2 GPa, for films deposited at 550degreesC and 450degreesC, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.