Fabrication of highly oriented lead-free (Na, K)NbO3 thin films at low temperature by sol-gel process

Lead-free piezoelectric (Na0.5K0.5)NbO3 (NKN) thin films were fabricated on SiO2/Si substrates by sol-gel process. The NKN precursor solution was prepared from Na-ethoxide, K-ethoxide, Nb-pentaethoxide, and 2-methoxyethanol. From thermogravinietry differential thermal analysis (TG-DTA) curve of the precursor dried-gel, weight loss and exothermic peaks appeared at about 300-500 degrees C at heating period. By using optimum fabrication conditions established from the TG-DTA, highly oriented single- phase NKN thin films were obtained at 500 degrees C by spin-coating technique. Average grain size and root mean square roughness obtained from atomic force microscope (AFM) image of the NKN thin film sintered at 500 degrees C were estimated to be about 250 and 8.35 nm, respectively. From TG curve, crystallinity and surface morphology, it is found that volatilization of alkaline elements seems to have been suppressible at temperature lower than 600 degrees C. (c) 2006 Elsevier B.V. All rights reserved.