Post-heat treatment effect on dielectric and optical properties of magnesium-based spinel

The current work reports the synthesis of magnesium aluminate spinel (MgAl₂O₄) using wet-chemical sol-gel technique at two different sintering temperatures of 900 °C and 1100 °C. The crystal structure of MgAl₂O₄ at both sintering temperatures was confirmed by X-ray diffraction. The obtained results showed the successful formation of MgAl₂O₄ along with some impurity peaks of magnesium oxide. Here, the crystallite size shows the linear nature with sintering temperature. The field emission scanning electron microscope (FESEM) shows the spherical shape. The change in morphology with sintering temperature is also confirmed by FESEM. Optical and electronic responses were studied by Fluorescence (FL) and electrochemical impedance spectroscopy (EIS). The FL study reveals that the prepared nanopowder tends to emit white light under the excitation wavelength of 350 nm. The intensity of emission peaks has been found to increase with sintering temperature, indicating an increase in defect states. Furthermore, using EIS data, the electrical parameters were studied in pellet form in the frequency range of 1 to 10⁶ Hz. The Nyquist plots have been successfully explained by employing LR[Q[R(CR)]] equivalent circuit corresponding to grain, grain boundary, and electrode contribution. The examined parameters have been significantly influenced by the sintering temperature. An increase in temperature is observed to result in higher values for the dielectric constant, loss tangent, and conductivity. Additionally, the electric modulus spectra reveal non-Debye behavior in the samples. The obtained results reveal that the prepared nanopowder can be used in optoelectronic devices, high-frequency equipment, and high-storage media.