Gas sensing properties of nanocrystalline tungsten oxide synthesized by acid precipitation method

Abstract WO 3 ·2H 2 O samples were prepared by acidic precipitation of sodium tungstate solution. Nanocrystalline WO 3 powders were obtained after 350 and 600 °C calcinations. XRD patterns of these samples showed a diffraction profile similar to that of monoclinic WO 3 . Calcinations at 600 °C yield WO 3 powders with particle sizes ranging from 60 to170 nm whereas that for 350 °C calcinations are in the range of 30–150 nm. The gas sensing properties of these powders in the form of thick film were investigated with and without platinum doping. Gas response of thick films sintered at two different temperatures was measured at four different operating temperatures. We confirm that the sensor elements made from 600 °C calcined powders doped with platinum sintered at 800 °C are highly responsive and selective to ammonia vapour at 350 °C operating temperature as compared to sensor elements made from commercial powders.