Preparation of gamma iron oxide particulate by a low temperature flux method

A simple technique, the low-temperature flux method, was developed to synthesize gamma-Fe/sub 2/O/sub 3/ directly from alpha-Fe/sub 2/O/sub 3/ in one step. A suitable modifier, including either alkaline or alkaline earth carbonates, was found to be a necessity for this process. The reaction rate and completeness of reaction as judged from X-ray diffraction were found to increase with temperature and amount of modifier used. One hour was found to be enough for a complete reaction in a flux of KCl+LiCl (in mole ratio of 0.43:0.57, the eutectic composition) at 650 degrees C using either calcium or barium carbonate at a molar ratio to alpha-Fe/sub 2/O/sub 3/ of 1:2. If the oxide-carbonate raw materials were mixed with the flux and heated up together, the resultant oxide was Fe/sub 3/O/sub 4/. However, if the raw materials were added into the flux melt kept at the reaction temperatures, the resultant oxide was gamma-Fe/sub 2/O/sub 3/. The particulate thus obtained was cuboid, hence the iHc was low.<
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