Submicron spindle and pseudocube α-Fe₂O₃ particles were synthesized at pH＝6～9 in the presence of trace Na₂SiO₃. In the current system, ferrihydrite was used as a precursor and FeCl₂ as a catalyst. The effect of initial pH, the concentration of Na₂SiO₃ as well as the forming conditions of the ferrihydrite on the phase transformation process and the morphology of α-Fe₂O₃ particles was studied, respectively. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to monitor the change in the synthesis process. The results show that Na₂SiO₃ inhibited the transfomation of ferrihydrite, which leads to the formation of the spindle or pseudocube α-Fe₂O₃ particles. Under the condition of weak alkalinity and [Si]/[Fe^3＋]＝0.01, the spindle (the axial ratio≥2) or pseudocube (300～400 nm) α-Fe₂O₃ particles were prepared and the formation mechanism of α-Fe₂O₃ particles was discussed.

Key words: Na₂SiO₃, catalytic synthesis, α-Fe₂O₃, spindle, pseudocube