CO₂ and CO Gas Sensing Properties of Submicron CoSb₂O₆ Wires Prepared by a Colloidal Method

Submicron CoSb₂O₆ wires were prepared by a non-aqueous colloidal method, using cobalt nitrate, antimony trichloride, dibutylamine and ethyl alcohol. Microwave radiation was used for solvent evaporation, producing a solid precursor material. X-ray powder diffraction, performed on calcined samples, revealed that single-phase CoSb₂O₆ was produced at 500 °C. CoSb₂O₆ wires, with length between 4 and 17 μm were observed by scanning electron microscopy (SEM). The observation by transmission electron microscopy (TEM) revealed that the surface of CoSb₂O₆ wires was covered by sharp and rounded points. By this technique, an average diameter of 170 nm was measured. CO₂ and CO gas sensing characterization was performed on thick films made with the as-prepared CoSb₂O₆ powder. The electrical measurements were performed in alternating current (AC), at 200 and 300 °C. At 200 °C, a significant variation of the magnitude of the impedance (|Z|) was registered in both gases. However, the best results were obtained at 300 °C, using a frequency of 100 kHz. The analysis of the results indicated that the gas sensing performance was better in carbon monoxide.