Self-assembly of α-Fe ₂O ₃ mesocrystals with high coercivity

This paper reports on the non-traditional corrosion method for the synthesis of hematite mesocrystals in the size range of 30 μm. The results clearly show that the self-assembly of hematite mesocrystals were consisted of many small building units which were densely packed. The formation mechanism for hematite mesocrystals is proposed, which belongs to nonclassical crystallization. Ammonium chloride (NH ₄Cl), as a reagent in the reaction, has played a key role in the formation of hematite mesocrystals. The high coercivity of hematite mesocrystals of 4437.80 Oe was recorded. The origin of the large coercivity is also discussed. The size of the building units is the main reason, the anisotropies of the mesocrystals, defects, strain and exchange coupling are attributed to the enhancement of the large coercivity. All of the reasons for the explanation of the large coercivity can be attributed to the presence of N. The synthesis route is economical and environmentally friendly and is a promising way to fabricate other kinds of mesocrystals.