Investigation on structural, optical, and electrical properties for sintered Mg-Zn aluminate systems

In the present work, the insulating MgAl2O4 and a semiconducting ZnAl2O4 were mixed as Zn0.5Mg0.5Al2O4 compound, which is synthesized by chemical co-precipitation method. We have investigated the structural, optical, and electrical properties for Zn0.5Mg0.5Al2O4 at different sintering temperatures. By X-ray diffraction (XRD) data analysis, the phase identification and intermediate phase formation were confirmed through the appearance of the superlattice peak at 2 theta = 49.1 degrees for (331) plane. The particle sizes of sintered samples were examined through high-resolution transmission electron microscopy (HRTEM) analyses. The weight percentages of Zn, Mg, Al, and O ions in the samples were obtained from EDX analysis. The cation distribution in the sintered Zn0.5Mg0.5Al2O4 samples was analyzed using solid-state nuclear magnetic resonance (SS-NMR) spectra. In addition, the UV absorbance spectra reveal an inter-bandgap region for the Zn0.5Mg0.5Al2O4 system. The optical bandgap was found to be a blue shift as observed from absorbance spectra on sintering. The frequency dependence impedance spectra and AC conductivity expose the contribution of grain, grain boundaries, and electrode-sample interface effects very clearly. The frequency dispersive nature of the dielectric constant and tan delta was measured and analyzed. The disparity observed due to the sintering of the sample was discussed and reported.