Effect of Hexagonal WO3 Morphology on NH3 Sensing

Abstract Tungsten oxide nano-powders were prepared by acidic precipitation from sodium tungstate solution. The alternative processes of the applied hydrothermal method resulted in different structure and morphology of hexagonal WO 3 nano-crystals. Micro-hotplates with gold electrodes on top to measure sensing layer conductivity were fabricated. WO 3 layers of the two morphologies were deposited using capillary dropping technique. Sensor responses were measured up to 220 °C operation temperature for NH3 diluted in synthetic air in the 10-100 ppm range. Test results are compared in terms of conductivity, sensitivity and response time.