W-Sn Mixed Oxides for Selective Detection of NO2

Tungsten-tin mixed oxides at increasing Sn molar fraction (0.1, 0.3 and 0.5) were synthesized by solgel co-precipitation route. The prepared powders were characterized by electron microscopy (SEM and TEM), X-ray diffraction, specific surface area measurements (BET), UV-Vis-NIR and IR spectroscopies. It turned out that the mixed materials W-Sn(0.1) and W-Sn(0.3) form a solid solution with WO3 crystal structure without phase segregation, achieving the goal to reduce the WO3 grain growth with temperature. The prepared powders were deposited to produce gas sensors in form of thick films through screen-printing technology. The gas sensing measurements highlighted that the mixed oxide sensors offer a better response with respect to pure WO3, at the same time maintaining the characteristics of almost complete insensitivity to carbon monoxide and benzene.