Gas sensing properties of nanoparticle indium-doped WO3 thick films

The gas sensing properties of pure and indium-doped nanoparticle WO3 thick films were studied. Sensors were prepared using commercial WO3 nanopowders and powder mixtures with different concentrations of In (1.5, 3.0 and 5.0wt.%). The gas sensing properties of the sensors to nitrogen dioxide, carbon monoxide, ammonia and ethanol were investigated. It was observed that the pure nanoparticle WO3 sensing layers began to react with nitrogen oxide at room temperature. These sensors had maximum sensitivity to NO2 at 100°C. The indium-doped WO3-based sensors were selective to NO2 and CO at 200 and 300°C, respectively. A mechanism for such behaviour is discussed.