Infrared and structural studies of Mg _1-xZn _xFe ₂O ₄ ferrites

Compositions of polycrystalline MgZn mixed ferrites with the general formula Mg _1-xZn _xFe ₂O ₄ (0≤x≤1) were prepared by the standard double sintering ceramic method. The structural properties of these ferrites have been investigated using X-ray diffraction and infrared absorption spectroscopy. The lattice parameter, particle size, bonds length, force constants, density, porosity, shrinkage and cation distribution of these samples have been estimated and compared with those predicted theoretically. Most of these values were found to increase with increasing Zn content. The energy dispersive (EDS) analysis confirmed the proposed sample composition. The scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs showed aggregates of stacked crystallites of about 200800 nm in diameter. Far infrared absorption spectra showed two significant absorption bands. The wave number of the first band, ν ₁, decreases with increasing Zn content, while the band, ν ₂ shifts linearly towards higher wave numbers with Zn contents, over the whole composition range. The room temperature electrical resistivity was found to decrease as Zn-content increases. Values of the vacancy model parameters showed that the packing factors P _a and P _b decrease, the fulfillment coefficient, α, remains almost constant and the vacancy parameter, β, strongly increases with increasing Zn content in the sample. The small values of P _a, P _b, α and the strong increase of the vacancy parameter, β, indicate the presence of cation or anion vacancies and the partial participation of the Zn ² vacancies in the improvement of the electrical conductivity in the MgZn ferrites.