Investigation of the structural, optical and electrical properties of ZnAl₂O₄

This work presents an investigation into the structural, optical, and electrical properties of ZnAl₂O₄ powder. The synthesis of this material was performed via an auto-combustion route. Then, structural characterization was carried out by XRD followed by Rietveld refinement of the obtained pattern, which indicates a normal spinel structure with the Fd3̄m space group, known as the Gahnite structure. This result was confirmed using RAMAN spectra recorded at room temperature, which exhibited two peaks corresponding to the Eg and T2g modes. After that, TEM microscopy proved the presence of semi-spherical particles with a size of about 45 nm. The optical properties from the PL emission spectra exhibit multicolor emission that can be attributed to defects and vacancies in the material. The electrical measurements of the prepared ZnAl₂O₄ sample prove the existence of semiconductor behavior following the Jonscher law at higher frequencies. At low frequencies, the dc conduction process was governed by the VRH process, while at high temperature it was assisted by the SPH mechanism.