Investigations of microstructural and impedance spectroscopic properties of Mg0.5Co0.5Fe1.6Al0.4O4 ferrite prepared using sol-gel method

Abstract Polycrystalline Mg0.5Co0.5Fe1.6Al0.4O4 ferrite was prepared with sol-gel method. This sample was characterized by powder X-ray diffraction (XRD), Scanning electron microscopy, and impedance spectroscopy. X-ray diffraction analysis combined with the Rietveld refinement confirmed that the sample crystallizes in a single-phase cubic spinel structure with (SG: \(Fd\stackrel{-}{3}m\)). 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” 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 a 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 (Rg) and grain boundary resistance (Rgb) with increasing temperature such as Rgb > > Rg. This result confirms that the transport mechanism for Mg0.5Co0.5Fe1.6Al0.4O4 compound is governed by the grain boundaries effect.