Synthesis of pure amorphous Fe₂O₃

A method for the preparation of pure amorphous Fe₂O₃ powder with particle size of 25 nm is reported in this article. Pure amorphous Fe₂O₃ can be simply synthesized by the sonication of neat Fe(CO)₅ or its solution in decalin under an air atmosphere. The Fe₂O₃ nanoparticles are converted to crystalline Fe₃O₄ nanoparticles when heated to 420 °C under vacuum or when heated to the same temperature under a nitrogen atmosphere. The crystalline Fe₃O₄ nanoparticles were characterized by x-ray diffraction and M¨ossbauer spectroscopy. The Fe₂O₃ amorphous nanoparticles were examined by Transmission Electron Micrography (TEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Quantum Design SQUID magnetization measurements. The magnetization of pure amorphous Fe₂O₃ at room temperature is very low (<1.5 emu/g) and it crystallizes at 268 °C.