Fine particles of cerium substituted hematite with different compositions were prepared by the sol-gel method from the aqueous solution of their corresponding metal salts. Mixed hydroxides of Fe and Ce were obtained by reacting aqueous NH with the aqueous solution of FeCl and Ce(NH ) (NO ) at pH 2.5-3.0) and they were heat treated at different temperatures between 400 and 1200°C in air for 2 h to get the mixed oxide product. Thermal analysis and X-ray diffraction studies revealed the coexistence of Fe O and CeO phase separately up to 900°C, and covalent interaction between them above 1000°C, which was evidenced by the shifting of the XRD peaks. Unit cell parameters and the cell volumes (V) of the samples derived between 1000 and 1200°C were found to be in the range a = 5.045-5.048 ± 0.007 Å, c = 13.774-13.815 ± 0.041 Å and V = 303.608-304.874 Å respectively. It was observed that both the lattice parameters and the cell volumes were higher than that of the pure α-Fe O (a = 5.036 Å, c = 13.749 Å, V = 301.976 Å ) system. The expansion of lattice parameters further supported the incorporation of the large Ce ion into the α-Fe O matrix. The lattice parameter increased with increasing Ce ion loading. FESEM studies showed the growth of the particles with increasing temperature though it was suppressed due to the presence of Ce ions as compared to the pure system. © 2005 Elsevier B.V. All rights reserved. 3+ 4+ 3 3 4+ 4+ 4+ 3 3 3 2 3 6 2 3 2 2 3 2 3