CuO doped WO3-SnO2 thick film gas sensors were fabricated by screen printing method on alumina substrates and heat-treated at 350℃ in air. The effects of mixing ratio of WO3 with SnO2 on the structural and morphological properties of WO3-SnO2 were investigated X-ray diffraction and Scanning Electron Microscope. The structural properties of the WO3-SnO2:CuO thick film by XRD showed that the monoclinic of WO3 and the tetragonal of SnO2 phase were mixed. Nano CuO was coated on the WO3-SnO2 surface and then the surface of WO3 was coated with SnO2 particles with 1~1.5 μm in diameters, as confirmed form the SEM image. The sensitivity of the WO3-SnO2:CuO sensor to 2000 ppm CO2 gas and 50 ppm H2S gas for the various ratio of WO3 and SnO2 was investigated. The 4 wt% CuO doped WO3-SnO2(75:25) tkick films showed the highest sensitivity to CO2 gas and H2S gas.
