WO3—Co3O4 Compositions Prepared by the Sol—Gel Process: Structure and Gas-Sensing Properties

The structure and phase features of the WO3−Co3O4 compositions prepared by the sol-gel process are studied by X-ray powder diffraction, IR spectroscopy, scanning electron microscopy, thermogravimetry, and by specific surface determination from low-temperature nitrogen adsorption in the temperature range 200–800°C. An appreciable rise is observed in the gas sensitivity of the compositions compared to the constituent oxides. The dependence of the CO and NO2 sensitivity on the two-phase composition is elucidated, and an explanation is given to the discovered trend. Low-power semiconductor sensors are manufactured, providing the determination of low nitrogen dioxide concentrations (<1 ppm) with good response and recovery times.