Impact of calcination temperature on the structural, electrical, and dielectric properties of sol–gel synthesized Ni_0.6Mg_0.2Co_0.2FeCrO₄ spinel ferrites

The impact of calcination temperature on the structural, electrical, and dielectric properties of Ni_0.6Mg_0.2Co_0.2FeCrO₄ spinel ferrites was investigated in this work. The sol–gel method was used to prepare two different samples (S850 and S950) at calcination temperatures of 850 °C and 950 °C, respectively. We used thermogravimetric analysis to investigate weight loss versus temperature and spinel phase formation. The average grain size and unit cell parameters increased with increasing calcination temperature. Grain and grain boundary contributions were found to govern the conduction process in the samples, as shown by Nyquist diagram modeling. The impedance and modulus curves revealed that the samples present dielectric relaxation phenomenon with non-Debye type. The CBH model has been used to explain the conduction process. As the grain size increased with rising calcination temperature, the activation energies decreased from 0.18 to 0.12 eV for S850 and S950, respectively. The conductivity isotherms were found to be almost merged into a single master curve according to Summerfield scaling. The high electrical resistivity of the Ni_0.6Mg_0.2Co_0.2FeCrO₄ samples makes them suitable for use in microwave absorption devices. Furthermore, the samples show low dielectric constants and dielectric losses at higher frequencies which is beneficial for their use in high-frequency applications.