Temperature-Dependent Dielectric Studies of Copper Cu and Magnesium Mg Doped Zinc Aluminate ZnAl₂O₄: Implications for Electrical Behaviour

This study focuses on studying the influence of copper Cu and magnesium Mg in Zinc Aluminate (Zn_0.9M_0.1Al₂O4: M= Cu, Mg) through comprehensive characterization. The samples were synthesized via sol-gel method followed by annealing at 900 degree celsius. Single-phase cubic spinel structure was confirmed using XRD. The lattice parameter and grain size were ascertained from the XRD data. Crystallite size determination of Cu and Mg-doped ZnAl₂O₄ using Scherrer’s formula was found to be in the range 25-40 nm. Confirmation of spinel structure formation was ascertained by FT-IR study. The optical properties of Cu and Mg-doped ZnAl₂O₄ were investigated using UV-Vis spectroscopy. The absorption spectra revealed characteristic absorption bands and allowed for the estimation of the bandgap energy. The optical bandgap values provided information about the electronic transitions and the potential application of the material in optoelectronic devices. The SEM images unveiled the generation of agglomerated particles with varying sizes and shapes. The presence of all the corresponding elements in the synthesized powders was assured using EDS analysis. Measurements of Dielectric parameters were performed in the broad frequency range (100Hz-1MHz) at temperatures varying from 25°C to 200°C. The results exhibited that the dielectric constant decreased with increasing temperature, while the dielectric loss exhibited a peak at a specific temperature. The Nyquist plots revealed semicircles, indicating the occurrence of grain and grain boundary contributions to the overall impedance response. The impedance analysis further indicated the presence of both bulk and grain boundary effects, with grain boundary contributions becoming more dominant at higher temperatures. The observed variations in dielectric properties and impedance responses can be attributed to the structural changes, such as grain growth and modifications in defect concentration, induced by temperature. These findings contribute to the understanding of the electrical behaviour of doped zinc aluminate materials and their useful applications in different electronic and energy systems.