Preparation and characterization of alpha-Fe2O3-CeO2 composite

Abstract

In our previous study we attempted to see the effect of cerium doping (Ce/Fe ratio 0.015 to 0.074) on goethite matrix and conversion of doped goethite to hematite. In the present communication, nano-structured alpha-Fe2O3-CeO2 composite with Fe/Ce weight ratio as 1.1 has been synthesized by calcination of goethite-cerium hydroxide precursor prepared by co-precipitation method. It was observed that co-precipitation of cerium along with iron in hydroxide medium resulted in hindering the formation of crystalline order as the precursor ;formed showed poorly crystallized goethite and almost no crystallinity in Ce(OH)(4). Calcination of the precursor at 400 degrees C showed the formation of hematite together with a broad peak corresponding to cerium oxide whereas at 800 degrees C, two distinct phases of alpha-Fe2O3 and CeO2 were observed. The Mossbauer spectra showed the presence of a paramagnetic component both for the precursor as well as for the sample calcined at 400 degrees C but on raising the calcination temperature to 800 degrees C, the paramagnetic component disappeared and the spectrum corresponding to pure alpha-Fe2O3 phase was observed. The microstructure of the product obtained by calcining at 800 degrees C showed rod like structure (30 to 50 nm width and 300 to 500 nm length) of alpha-Fe2O3 having equi-dimensional CeO2 particles on and around the surface. Besides the rods, equi-dimensional particles and agglomerates corresponding to CeO2 were also observed. The results show that co-precipitation followed by calcinations gives nanorods hematite with CeO2 particles bonded to its surface. (C) 2008 Elsevier Inc. All rights reserved.