Development of a WO3 thick-film-based sensor for the detection of VOC

A highly sensitive gas sensor for the detection of aromatic hydrocarbons has been developed using a WO3 thick film where Pd and Pt were applied as catalyst to a limited and most sensitive area of the film to the change in bulk resistance. WO3 thick films with different mean grain size and film thickness were prepared to investigate characteristics of the films to aromatic hydrocarbon gases at various operating temperatures. The film operated at 400 °C with mean grain size of 85 nm and thickness of 35 μm was found to be ideal for the detecting target gases. The sensitivities of the sensor were investigated by measuring toluene, ethylbenzene, styrene and m-xylene at a concentration range of 10-1000 ppb and some of interference gases at a range of 0.1-500 ppm. The sensor showed extremely high sensitivities to the aromatic hydrocarbon gases, and the changes in the film resistance were more than two times even at concentration of 10 ppb. By contrast, the sensor showed very low sensitivity to the interference gases.