Preparation and gas sensing properties of pure and doped γ-Fe2O3 by an anhydrous solvent method

Nanocrystalline undoped and Cd-doped γ-Fe2O3 powders were synthesized by an anhydrous solvent method 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 5 mol% Cd-doped γ-Fe2O3 sensors (operated at 270 °C) exhibited high response to acetone and ethanol, moderate response to petrol, poor response to liquefied petroleum gas (LPG), H2 and CO. Furthermore, the 5 mol% Cd-doped γ-Fe2O3 sensor presented shorter response and recovery times, better long-time stability, larger response and better selectivity to acetone and ethanol than the undoped sensor. The present undoped and Cd-doped γ-Fe2O3 sensors obtained by an anhydrous solvent method were almost insensitive to LPG, while the reported γ-Fe2O3 sensors prepared by a hydrous solution method were generally sensitive to LPG, suggesting that the preparation method played a key role in determining the gas sensing properties.