Formation mechanism of β-Fe2O3 particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO4)2 and Na3Fe(SO4)3 to NaCl and the heat treatment temperature. The heat treatment temperature strongly affected the particle shapes and sizes. β-Fe2O3 was found to be formed by two different reactions; one is a solid state reaction below 490 °C, and another is a liquid phase-mediated reaction above 490 °C. β-Fe2O3 had granular shape with a diameter of about 50 to 100 nm below 490 °C, while at high temperatures above 490 °C cubic particles with relatively large size of about 500 nm to 2 μm were produced. We found that this dramatically change of particle morphology including their sizes and shapes was caused by the effects of the liquid phase in the reaction.
