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

Copper (Cu2+)-and-magnesium (Mg2+)-doped Zinc aluminate ZnAl2O4 is a promising material with diverse applications in electronic and energy storage devices. In this study, the synthesis of Zn0.9MxAl2O4 (M = Cu2+ and Mg2+; x = 0.00 and 0.10) was conducted via the sol–gel combined combustion technique. The structural, spectral, optical and dielectric parameters of the synthesized spinel aluminates were analysed to explore the substitution effect of Cu2+ and Mg2+ content. The formation and crystallinity analyses of the single-phase cubic spinel structure in the synthesized spinel aluminates were confirmed using XRD patterns. The lattice parameter and grain size were ascertained from the XRD data. The crystallite size of Cu2+ and Mg2+ substituted into ZnAl2O4 using Scherrer’s formula was found to be around 22 nm. The spinel structure formations in the prepared spinel aluminates were ascertained through an FT-IR study. The UV-Vis spectra exhibited a broad absorption band in the UV-Vis region, indicating the presence of electronic transitions. The band gap energy of the prepared aluminates was estimated from the absorption edge, with values varying between 2.90 eV and 3.03 eV, revealing its suitability for optoelectronic applications. Measurement of the dielectric parameters was performed in the frequency range of 100 Hz to 20 MHz at temperatures ranging from 30 °C to 250 °C. The dielectric constant (ε′) and dielectric loss (ε”) were determined as a function of frequency at different temperatures. The results showed that the dielectric constant decreased with increasing frequency for all the observed temperatures, while the dielectric loss exhibited a peak at a specific temperature. The conductivity results indicate that the conduction mechanism occurred due to polaron hopping. The Arrhenius relation was adopted to calculate the activation energies Ea for all the samples, and the values were between 0.70 eV and 0.38 eV. The obtained results were discussed and interpreted. These findings contribute to our understanding of the electrical behaviour of doped zinc aluminate materials and their useful applications in different electronic and energy systems.