Effect of the frequency on the gas sensing response of CoSb2O6 prepared by a colloidal method

CoSb2O6 with trirutile-type structure was prepared by a colloidal method using cobalt nitrate hydrate, antimony trichloride, ethylenediamine and ethyl alcohol. To obtain a precursor material, microwave radiation was applied during the evaporation process. The thermal decomposition of the precursor powder at 600 °C produced single-phase polycrystalline CoSb2O6. By scanning electron microscopy a widespread formation of microcolumns, having a length in the range of 6–18 μm, and an average diameter of 2.5 μm were observed. The gas sensing properties of CoSb2O6 thick films was evaluated by measuring the transient response of the magnitude of the impedance (|Z|) in air, CO2 and O2. This characterization was made at 100 Hz, 1 kHz and 100 kHz (400 °C). The results indicated that increasing the frequency, smaller |Z| values were registered. However, a lot more uniform and noise-free response during the detection of these gases was obtained. Polarization curves demonstrated that CoSb2O6 responds quantitatively to changes in the CO2 concentration. However, in O2 this behavior was not observed.