Infrared spectral studies of nanostructured Co2+-substituted Li-Ni-Zn ferrites

Polycrystalline Li0.5Ni0.25–0.5x Co0.5x Zn0.5Fe2O4 ferrites (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared by standard auto-combustion method and characterized by XRD and IR spectra. The XRD results suggest that all samples were single-phase with a cubic spinel-type structure. The lattice constant, particle size, metal-oxygen bond length (R A and R B), cation radii (r A and r B) on A and B-sub lattices were found to increase while the X-ray density and porosity, decrease with increasing x. The IR spectra show two absorption bands, at ν1 about 600 cm−1 and ν2 at about 425 cm−1, which were attributed to tetrahedral (A) and octahedral (B) sites of the spinel structure, respectively. The band positions were found to depend on x. The force constants, K t and K o, were calculated and plotted against cobalt concentration x. Compositional dependence of the force constants is explained in terms of cation-oxygen bond distances and redistribution of cations.