Investigation of Transition metal ion Cu²⁺ and Mg²⁺ Doped Zinc Aluminate (ZnAl₂O₄) and their Structural, Spectral, Optical, and Dielectric study for Storage applications.

Spinel bimetallic oxides nanomaterials have attracted attention due to their unique crystal structure, excellent optical and dielectric properties, high chemical and thermal stability, low surface acidity, etc. As a typical spinel semiconductor with wide band gap (E_g = 3.8 eV), Zinc aluminate (ZnAl₂O₄) has been widely investigated in the field of catalysis, hydrogen storage, sense, display. It has also attracted attention as a phosphor carrier material for use in thin-film electroluminescent displays, mechano-optical voltage sensors and voltage visualization devices. Herein, Zn_1-xCu_0xAl₂O₄ (x = 0.00 and 0.10) has been synthesized through the sol–gel auto combustion technique. The structural, spectral, optical, morphological and dielectric properties of the synthesized nanoparticles were analyzed. The X-ray diffraction analysis revealed the single phase spinel structure. The crystallite size in the range of 55-65 nm was ascertained by the Scherrer formula. The substitution of copper and magnesium in Zinc spinel aluminates was found to have a significant effect on crystallite size, lattice strain, micro-strain and dislocation density. Transition metal ion doped aluminates samples evinced a decrease in the optical band gap energy from E_g = 3.36 to 3.20 eV. Surface morphology of the materials has been studied through the HRSEM-EDX analysis. The dielectric properties were explored in the frequency range 1 Hz to 10 MHz. Impedance study revealed the grain boundaries to be dominant as a function of Cu²⁺ and Mg²⁺ content. Inverse relation of ac frequency with the dielectric constant exposed the existence of Maxwell–Wagner type interfacial polarization. The conducting and resistive grain boundaries play a vital role in understanding the dielectric relaxation in the material. From the observed electrical parameters, it can be propounded that the prepared spinels hold semiconducting nature and can be employed as a dielectric in low-frequency devices. They also serve as potential candidate in optoelectronics, magnetic and catalysis applications.