Optimizing Magnetic, Mechanical, and Electrical Properties of Cobalt-Substituted Zinc Chromite Spinel via Microwave-Hydrothermal Synthesis

Using the microwave-hydrothermal technique, researchers synthesized a cobalt-substituted zinc chromite spinel structure with the formula Zn_1 − xCo_xCr₂O₄ (x = 0.0, 0.25, 0.50, 0.75, 1.0). The resulting powder underwent analysis via X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) to determine the ideal conditions for eliminating organic components from the fired pellet. After establishing the optimal initial calcination temperature, all powder samples were calcined at 600 °C, then compressed and fired at 1300, 1400, 1500, and 1600 °C. The fired pellets were then examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Additionally, researchers evaluated the pellets’ physical, electrical, dielectric, magnetic, and mechanical properties. The findings indicated that 1600 °C was the optimal firing temperature for the pellets. The apparent porosity decreased, and the bulk density increased with increasing Co content and firing temperature. Enhancements in magnetization, mechanical, and electrical conductivity, dielectric properties, and elastic moduli were observed by increasing the cobalt content. Porosity has a significant impact on mechanical properties. The mechanical properties were slightly reduced for zinc-rich pellets. The dielectric constant and the dielectric loss increased with increasing Co content at 1 MHz. In addition, the results show that the dielectric constant and dielectric loss factor decreased with increasing frequency, whereas the A.C. electrical conductivity increased with increasing frequency.