Homogeneous Precipitation of Uniform alpha-Fe2O3 Particles from Iron Salts Solutions in the Presence of Urea.

Uniform alpha-Fe2O3 particles within the nanometer range (100-300 nm) have been obtained by precipitation of iron (III) perchlorate in the presence of urea. Different morphology, from spheres to ellipsoidal particles with axial ratio up to approximately 10, was obtained by adding to the initial solution increasing amounts of phosphate anions up to 7 x 10(-3) M. The main targets of this work are the reduction in particle size and precipitation time and the increase of the particles axial ratio, keeping a narrow particle size distribution, in comparison to other methods previously developed to obtain homogenous alpha-Fe2O3 particles. A detailed analysis of the reaction products and a systematic study of the influence of the different precipitation conditions on the characteristics of the resulting particles have been carried out. Finally, some information on the formation mechanism of the ellipsoidal hematite particles in the iron (III) salt-urea-phosphate system is also given. Copyright 1999 Academic Press.