A Metastable Ion (III) Oxide Phase (ε-Fe2O3): Preparation and Gas Sensing Properties

ε-Fe₂O₃ is a rare and metastable iron (III) oxide phase. ε-Fe₂O₃/SiO₂ composites were prepared by combining the reverse-micelle and sol-gel methods. An appropriate amount of Ba²⁺ was needed in this system to promote the formation of ε-Fe₂O₃ nanorods in SiO_2. The size of nanorods varied with different Ba²⁺ addition amount and sintering procedure. Then pure ε-Fe₂O₃ nanorods were obtained after stripping SiO₂ by etching due to NaOH aqueous solution. The as-synthesized ε-Fe₂O₃ nanorods were discussed using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Interestingly, metastable ε-Fe₂O₃ nanorods showed a promising performance for the response for ethanol, compared with the stable phases of α-Fe₂O₃ and γ-Fe₂O₃. It indicates that nanostructure ε-Fe₂O₃ (including ε-Fe₂O₃ nanorods) could be a valuable material for the fabrication of advanced sensing devices.