Infrared studies of some mixed Li–Co ferrites

The infrared spectra of Li–Co mixed ferrites with the general formula Li_0.5−x/2Co_xFe_2.5−x/2O₄ (where x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7) have been analyzed in the frequency range 200–800 cm⁻¹. The single phase formation of ferrites was confirmed by X-ray diffraction studies. The IR spectra revealed four absorption bands for the sample x=0.1 and x=0.2. The sample with x=0.3 and 0.4 exhibit three absorption bands and the samples with x>0.4 show two prominent absorption bands. The IR bands are attributed to the fundamental vibrational modes of tetrahedral and octahedral complexes of the unit cell. The IR band due to tetrahedral complexes is found to be shifted slightly towards high frequency side where as that due to octahedral complexes is found to shift towards lower frequency side. The bands do not show splitting indicating no excess formation of Fe²⁺ ions.