DIELECTRIC-DISPERSION IN ALUMINUM-DOPED ZINC MANGANESE FERRITES

The dielectric constant epsilon, loss tan delta, and conductivity sigma of aluminium doped zinc-manganese ferrites of general formula Zn0.3Mn0.7Fe2-xAlxO4 (with x values ranging from 0.2 to 1.0) are studied as a function of frequency, in the range 5 to 500 kHz and in the temperature range 30 to 150-degrees-C. All these samples are found to exhibit dipolar relaxation effects. The variations in epsilon and tan delta with frequency and temperature are observed to be strongly dependent on the concentration of aluminium. The results are explained on the basis of the Verwey mechanism involving hopping of electrons in the spinel structure.