Spectroscopic analysis of defect-induced luminescent and dielectric properties of MgO-based composites on varying dopant concentration

In this novel study, we prepared MgO matrix composites reinforced with varying weight percent ZnO using a solid-state reaction (SSR) method at 500 degrees C. We aimedto explore the potentialof these composites for highfrequency electronic devices.We conducted a comprehensive structural analysis of these MgO-based composites using various spectroscopic and microscopic techniques. Thisinclusive analysis revealed the morphology, particle size, elemental composition, valence states of elements, and defects in the composites. The Rietveld refinement of XRD data confirmed the presence of binary phase and the phase % of the constituents of composites. XPS spectra demonstrated the isovalent character of Zn/Mg elements and the presence of lowcoordinated oxygen ions at the surface of the composites. The UV - visible-based spectroscopic techniques (Absorption and Photoluminescence) further supported the presence of low-coordinated surface O 2 - ions and Fcenter defects that caused a significant reduction in the bandgap of the samples. Photoluminescence (PL) analysis suggested the passivation of F-center defects in composites. We also investigated the effect of ZnO concentration and multiple excitation energies on the site-specific localized F-center defects to understand the defect distribution in the composites relative to the host. The dielectric properties of ZnO/MgO composites were assessed through impedance spectroscopy. We observed a significant enhancement in the dielectric constant (- 28.69 - 32.60) of the composites compared to pure MgO (-12.2) at 1 kHz. This enhancement along with the smaller impedance of the composites relative to the host, as endorsed by the PL results,suggests areduction in F-centers (electrical barriers). This exciting finding paves the way forthe synthesis of ceramic composites with excellent dielectric and optical properties, indicating their potential applications in high-frequency electronic devices.