Dielectric properties and D.C. resistivity of magnesium-substituted lithium ferrites

The paper reports the influence of magnesium substitution on structural and electrical properties of lithium ferrites. The samples with compositional formula Li/sub (1-x//2)Mg/sub x/Fe/sub (5-x//2)O/sub 4/ with x ranging from 0.1 to 0.9 were prepared by standard dry ceramic method. XRD shows all the samples to be single phase spinel and the value of lattice constant was found to increase with increasing substitution level x. The room temperature d.c. resistivity increases with x. The variation has been explained in terms of hopping mechanism and the cation distribution. The resistivity with temperature shows a change in slope which does not correspond to Curie temperature. The activation energy determined from the slopes in two temperature regions shows a large difference. It has been interpreted in terms of two conduction mechanisms i.e. ionic and electronic. The dielectric measurements were carried out at room temperature in the frequency range 10 kHz to 10 MHz. Dielectric constant shows a dispersion with frequency for all the samples. The dielectric loss decreases with frequency and does not show any peak with frequency for any of the samples.