Abstract
Polycrystalline Mg0.5Co0.5Fe1.6Al0.4O4 ferrite was prepared using sol-gel method. This sample was characterized by powder X-ray diffraction (XRD), Scanning electron microscopy, and impedance spectroscopy. XRD analysis combined with the Rietveld refinement confirmed the cubic-spinel structure (SG: Fd(3)(-)m) for the prepared sample. Electrical conductivity obeying the Jonscher power law indicates that the prepared material exhibits semiconductor behavior, and the conduction process follows the "non-overlapping small polaron tunnelling, NSPT" model between neighbors' sites. The behavior of dielectric constants such as permittivity and loss coefficient has been interpreted based on the Maxwell-Wagner's theory of interfacial polarization. The curves of imaginary parts of impedance (Z '') and modulus (M '') show dielectric-relaxation phenomenon in the sample with activation energy near to that determined from the dc conductivity study. Nyquist plots (- Z '' vs. Z ') show a monotonic decrease in both grain resistance (R-g) and grain boundary resistance (R-gb) with increasing temperature such as R-gb >> R-g. This result confirms that the transport mechanism in Mg0.5Co0.5Fe1.6Al0.4O4 compound is governed by the grain boundaries effect.