Sol-gel derived pure and palladium activated tin oxide films for gas-sensing applications

Pure and Pd activated SnO2 films on Coming 7059 substrates were prepared by the sol-gel dip coating method and used as active material in gas-sensing devices. SnCl4 and Pd(CH3COO)(2) were used for tin and palladium sources. The SnO2 sol was prepared from 1:3:9:4 molar ratios of SnCl4:H2O:(C3H7OH)-H-n:(C4H9OH)-H-i. The 5 equivalent wt% PdO-95% SnO2 sol was prepared by mixing the required amount of Pd acetate to the pure SnO2 sol. The dried (110 degrees C/0.5 h) films were heat-treated in air at 600 degrees C for 1 h. Pure SnO2 films showed ethanol gas sensing characteristics similar to most of the commercially available tin oxide sensors. An improvement in the sensitivity towards ethanol gas at relatively low temperature was observed in case of Pd activated SnO2 films. The improvement of sensing properties of Pd activated films was due to high surface roughness/surface area, oxygen vacancies and presence of PdO microcrystallites. (C) 1999 Elsevier Science S.A. All rights reserved.