Structural and dielectric behaviors for Mg_0.5Co_0.5Fe₂O₄ spinel ferrite synthesized by sol–gel route

In this work, the structural and dielectric properties for Mg_0.5Co_0.5Fe₂O₄ ferrite (abbreviated as MCFO) prepared by sol–gel process were investigated. The XRD characterization for this sample confirmed the development of the face-centered cubic spinel structure with Fd3 ¯ m space group. The Nyquist plots are well modeled by an equivalent electrical circuit made up of a combination of grain and grain boundary elements. The behavior of dielectric constants has been interpreted based on the Maxwell–Wagner’s theory of interfacial polarization. Electrical properties show that the sample exhibits higher electrical resistivity. The non-overlapping small polaron tunneling and the correlated barrier hopping are the suitable models to describe the conduction process for the sample. The conductivity spectra do not follow both Ghosh scaling and Summerfield scaling. The random barrier model (RBM) is applied to correct the Summerfield scaling. According to this model, the conductivity isotherms for the MCFO ferrite are almost merged into a common curve with negative values of the scaling parameter α. This indicates that the conductivity comes from non-interacting particles. The behaviors of imaginary parts of impedance (Z″) and modulus (M″) show dielectric-relaxation phenomenon in the sample with activation energies near to those determined from the conductivity study.