Sol–gel synthesis and comprehensive characterization of MgO nanostructures: structural, optical, and dielectric insights

Abstract

MgO nanostructures synthesized via the sol–gel method were examined for their structural, microstructural, optical, and dielectric properties. XRD indicated a crystalline cubic phase with an average crystallite size of approximately 30–50 nm, corroborated by TEM findings of quasi-spherical to polyhedral morphologies. Mapping of electron density distribution validated the face-centered cubic structure, while the modified Scherrer, Williamson-Hall, size-strain plot, and Halder-Wagner methods indicated peak broadening attributable to lattice strain and stacking faults. Optical measurements indicated a reduced band gap of approximately 4.48 eV compared to bulk MgO, attributed to surface states, oxygen vacancies, and quantum confinement effects. The Urbach energy (approximately 168 meV) enhanced the identification of defect-related localized states within the band gap. AC conductivity increased with frequency, supporting Jonscher’s universal power law, whereas impedance spectroscopy revealed grain-dominated dielectric relaxation exhibiting non-Debye behavior in the Cole–Cole plot, characterized by a single semicircular arc. Frequency-dependent dielectric constant and loss demonstrated interfacial and dipolar polarization. This study is the inaugural investigation to directly associate microstructural defects and strain from the synthesis process with the optical and electronic transport properties of the material, demonstrating the sol–gel method’s capability for fabricating functional ceramics with customized attributes for advanced electronic and optoelectronic applications.