Synthesis of octahedral magnetite microcrystals with high crystallinity and low coercive field

Octahedral magnetite microcrystals were synthesized through a facile hydrothermal approach at 140 °C using potassium ferrocyanide (K4Fe(CN)6) and sodium borohydride (NaBH4) as starting materials. The structure and morphology of as-prepared particles were characterized by X-ray power diffraction (XRD), Raman spectrum and field emission scanning electron microscopy (FE-SEM). The results showed that magnetite particles, with size ranging from 2 to 5 μm, are octahedral in shape. It is found that the concentrations of NaBH4 and NaOH have great influences on the formation of octahedral magnetites. Compared with the bulk magnetite and some magnetite nanoparticles, these octahedral microcrystals possessed higher saturation magnetization (102.57 emu/g) and lower coercive field (12.55 Oe). Possible reasons were discussed, based on the morphology, crystallinity and microstructure of the particles.