Combustion synthesis, structure and magnetic properties of Li-Zn ferrite ceramic powders

We report the effect of Zn-substitution on the structure and magnetic properties of Li-ferrite powders (Li0.5-x/2ZnxFe2.5-x/2O4, x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) synthesized by combustion synthesis route. Different stages involved during progress of combustion synthesis of Li-Zn ferrite samples were monitored by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The scanning electron micrographs of the synthesized samples show foamy network type of morphology with rod-shaped particles. Rietveld refinement of the X-ray diffraction (XRD) data confirmed the preferential occupancy of the Zn-atoms at the tetrahedral sites and the Li atoms at the octahedral sites of the spinel structure. Trace amounts of zinc-oxide and iron-oxide impurity phases were found for the samples with high Zn content (x >= 0.6). The comparison of the particle sizes obtained from scanning electron micrographs and the crystallite sizes estimated from XRD results suggest that the particles are polycrystalline aggregates of a few crystalline grains. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of broad (vibrational) absorption bands between similar to 510 and 800 cm(-1) (v(1)) corresponding to tetrahedral complexes and between similar to 250 and 510 cm(-1) (v(2)) corresponding to octahedral complexes in the spinel structure of the Li-Zn ferrites. The phase compositions of the samples were obtained from the analysis of Mossbauer spectra and XRD patterns. Substitution of higher amount of Zn2+ ions reduces the saturation magnetization of the samples. Our work demonstrates that combustion synthesis method is a cost effective and simple way to synthesize bulk amount of Li-Zn ferrite samples with desired physical properties.