Site occupation study of ZnFe2O4 and NiFe2O4 by far-infrared reflectivity

ZnFe2O4 and NiFe2O4 ferrite ceramics were prepared by conventional solid phase reaction using high purity reagents. The far-infrared reflectivity for these ferrites was investigated. The observed reflectivity spectra were fitted to four IR active modes predicted by the factor group analysis, in order to estimate the vibration frequencies. Eigenfrequencies of the lattice vibrations and effective charges of the ions were calculated in order to determine the site occupation factors of the divalent cations. These were compared with data obtained from Rietveld analysis of X-ray diffraction spectra. The effective charges of the ions were close to the ionic valence for all ions. The occupation factors of Zn, Ni, and Fe ions were close to values reported by other researchers. However, it was found that a small fraction of Ni ion also occupied the A site in the Ni ferrite. (C) 2004 Elsevier B.V. All rights reserved.