AC conductivity, complex impedance and photocatalytic applications of Co²⁺ substituted Mg–Zn nanoferrite

Abstract

This paper is focused on the investigation of dielectric parameters, optical properties, and photocatalytic activity of Mg_0.8Zn_0.2−xCo_xFe₂O₄ (MZCFO) nanoferrites upon the substitution of Co²⁺ ions range (0 ≤ x ≤ 0.2; step 0.04). The dielectric constant, dielectric loss, and ac conductivity variations, with frequency for all MZCFO samples, can be interpreted based on Maxwell–Wagner interfacial polarization. The lowest value of dielectric loss (~ 0.45) was recorded for the ferrite sample, with x = 0.08 at room temperature and a frequency of 5 MHz. The dielectric constant, dielectric loss, and ac conductivity were found to adopt a climbing trend with raising the temperature. The impedance formalism showed a decrease in the grain boundaries resistance (R_gb) with increasing Co²⁺ content and was calculated by implementing the Cole–Cole plot. The UV–Vis spectrum, along with Tauc’s equation, was used to estimate the bandgap of MZCFO ferrite nanoparticles, which was found to tune successfully with the addition of Co²⁺ ions from 1.96 to 1.81 eV. This finding gives escalation to the enhancement of photocatalytic activity, and degradation efficiency of MB dyes under the illumination of visible-light experiences an increase from 65 to 95% with increasing the addition of the nanoferrite with (x = 0.2). The optimum properties of the nanoferrite Mg_0.8Co_0.2Fe₂O₄, such as the high dielectric constant along with high conductivity, besides its ability for MB degradation, and so a peak success in water-treatment applications is predicted.