WO3 and W-Ti-O thin-film gas sensors prepared by sol-gel dip-coating

The WO3 and W-Ti-O thin-films were prepared by sol-gel dip-coating on alumina substrate using tungsten chloride, 2,4-pentanedione (PTN), ethanol and water as sources and calcined at 400 degreesC. The structure was characterized by XRD, Raman, SEM and TEM analyses. The effect of titanium doping on the structure was then discussed and related to the gas sensing properties. The results show that the sensitivities for detecting 10 ppm NO2 were 82 and 1768 by WO3 and W-Ti-O gas sensors at 200 degreesC, respectively. The huge increase in sensitivity by adding titanium ion arose from the grain size reduction of the films and the doping effect on Debye length. The improved sensitivity, recovery, and reliability suggest that WO3 and W-Ti-O thin-films prepared by sol-gel dip-coating can be used for NO2 gas sensing. (C) 2002 Elsevier Science B.V. All rights reserved.