Preparation of tungsten oxide–tin oxide nanocomposites and their ethylene sensing characteristics

A novel method for preparation of WO3–SnO2 nanocomposite was described. 0.3–10.0 wt.% WO3 was incorporated into the SnO2 powder by precipitation of hydrated WO3 from ammonium tungstate precursor solution containing SnO2 powder. This preparation method resulted to uniform mixing of ∼35 nm WO3 and ∼100 nm SnO2 nanoparticles as revealed by direct observation using a transmission electron microscope, and by performing elemental dot mapping. Upon calcination to 500 °C, both cassiterite SnO2 and monoclinic WO3 were stable, and no other crystalline phase was observed. To evaluate gas sensing performance, the powders were formed into thick-film sensors using a screen printing technique. It was found that the gas sensitivity of the SnO2 base was enhanced when very small amount of the WO3 (0.3 wt.%) was incorporated. The 0.3 wt.% WO3–SnO2 sensor was very sensitive to 2–8 ppm ethylene at optimum operating temperature of 300 °C. The sensitivity decreased with increasing amount of the WO3.