The inflence of the additives, NaH2PO4 and 1-hydroxyethylidene-1,1’-diphosphonic acid (HEDP), the concentration of HNO3 and the temperature of reaction on the phase transfor-mation and aggregation of Fe2O3 particles obtained by the boiling reflux of 0.2mol-1 Fe(NO3)3 solution has been studied using TEM and XRD. Phosphate gave monodispersed spindle-shaped α-Fe2O3 perticles used as magnetic recording material. Nanowhiskers of α-Fe2O3 was formed in the presence of HEDP and HNO3. The method is provisionally referred to as the inhibitory sub-crystal aggregation method.
Cubic and ellipsoide ultrafine monodispersed hematite colloidal particles wereprepared by hydrothermal reaction from Fe（OH）3 get in the presence of Sn4+ ions. Thenumbers of nuclei increase with the concentration of Sn4+ ions. The initial concentrationof Fe（OH）3 gel might approach to 0.5 mol.L- 1. The products were characterized by TEMand XRD.
