Synthesis, characterization and gas sensing properties of undoped and Co-doped γ-Fe2O3-based gas sensors

Nanocrystalline undoped and Co-doped γ-Fe2O3 powders were synthesized by an anhydrous solvent method for the first time and characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron micrograph (TEM). The gas sensitivity measurements indicated that both the undoped (operated at 240 °C) and the 12 mol% Co-doped γ-Fe2O3 sensors (operated at 270 °C) exhibited high response to acetone and ethanol, moderate response to petrol, poor response to CH4, H2 and CO. Compared with the undoped, the 12 mol% Co-doped γ-Fe2O3 sensor presented shorter response and recovery times, larger response and better selectivity to acetone and ethanol, suggesting that the improvement in gas sensing performance is mainly attributed to the nature of Co addition and the relative mechanism is also discussed in detail.