The composite, consisting of two materials with different sensing temperatures, may show the selectivity for a particular gas. In this study, the microstructural and compositional effects on the electrical conductivity and the CO and the H2 gas sensing properties of SnO2-TiO2 composites were examined. SnO2-TiO2 composites in entire (0–100 mol%) composition range were fabricated in the form of porous pellet by sintering at 800°C for 3 h. The effects of CuO-coating (or doping) on the electrical conductivity and the sensing properties to 200 ppm CO and H2 gases were examined.
With CuO-coating, SnO2-TiO2 composites showed the increased sensitivity to CO gas and a large difference in the sensing temperatures between CO and H2 gases. As a result, CuO-coated SnO2-TiO2 composites showed the selectivity for CO gas between 100°C and 190°C and the selectivity for H2 gas between 280°C and 380°C.