Al-for-Fe substitution in hematite: the effect of low Al concentrations in the Raman spectrum of Fe2O3

Five different mixed Al-hematites with an aluminium molar content varying from 0 to 10% were investigated by micro-Raman spectroscopy to study the effect of Al-for-Fe substitution on the hematite lattice. A red shift of hematite vibrational wavenumbers and a line broadening were observed; also a shoulder located near 430 cm(-1) and a broad band at 670 cm(-1) developed. The variation of the spectral features is discussed in terms of a local disorder correlated to the insertion of Al3+ ions into the Fe(O)(6) octahedra constituting hematite structure. A multivariate analysis was also carried out on the spectral data to distinguish between the doped samples analysed. Copyright (c) 2007 John Wiley & Sons, Ltd.