Preparation and Formation Mechanism of Different α-Fe₂O₃ Morphologies from Snowflake to Paired Microplates, Dumbbell, and Spindle Microstructures

Different morphologies of α-Fe₂O₃ crystals including snowflake-like, paired microplates, dumbbell, column, and spindle microstructures have been prepared though a hydrothermal reaction in K₃[Fe(CN)₆] solution with different pH values at 140 °C. The influences of the experimental conditions, such as pH value and reaction time on the morphologies of the as-prepared α-Fe₂O₃ crystals, have been studied. The morphologies and structures of the α-Fe₂O₃ crystals have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Selected-area electron diffraction confirms that the snowflake-like microstructure and paired microplates grow along the [001] direction, respectively. A possible growth process of α-Fe₂O₃ crystals with varied morphologies from sixfold snowflake-like to the column-like microstructure has been proposed. Additionally, magnetic investigations show that the α-Fe₂O₃ crystals with column-like microstructures exhibit a weakly ferromagnetic property at room temperature.