Study of Thermal, Structural, and Above-Room-Temperature Dielectric Properties of Mg-Cd-Cu Spinel Ferrites Under Different Annealing Temperatures

The effects of annealing temperature on the thermal, structural, and dielectric properties of spinel ferrites Mg_0.4Cd_0.3Cu_0.3Fe₂O₄ were studied in this work. Two specimens were prepared by the sol–gel technique under different annealing temperatures (850°C and 950°C). Rietveld analysis of x-ray diffraction data revealed a well-formed cubic spinel structure. An obvious correlation was found between the unit cell parameters and the calcination temperature. Thermogravimetric analysis was used to examine the formation of spinel phases and the correlation between temperature and weight loss. Analysis of Nyquist diagrams indicated that the conduction mechanisms of the samples were influenced by the grains and grain boundaries. Electrical conductivity studies revealed semiconductor behavior in the samples, consistent with the correlated barrier hopping (CBH) model. Moreover, the materials exhibited reduced dielectric constants and dielectric losses at high frequencies. The ability of Mg_0.4Cd_0.3Cu_0.3Fe₂O₄ spinel ferrites to transmit and store electrical energy in this frequency range makes them ideal candidates for high-frequency applications. In addition, the samples exhibited elevated electrical resistivity, emphasizing their potential suitability for use in microwave devices.