Defect modulation and color tuning of MgO: Probing the influence of Sm and Li dopants through x-ray absorption, photoluminescence, and thermoluminescence spectroscopy

Abstract

Pure, singly doped (Sm), and co-doped (Sm, Li) MgO nanoparticles have been prepared using the solution combustion method. X-ray diffraction (XRD) analysis has revealed the development of microstrain, alteration in the unit-cell parameters, and dislocation/defect densities in the MgO lattice as a function of Sm and Sm+Li doping. Transmission electron microscopy (TEM) images and selected area electron diffraction (SAED) patterns illustrate the formation of polycrystalline samples ranging from 45 nm to 65 nm in size. X-ray absorption near-edge structure (XANES) spectroscopy at Sm L-edge confirms the presence of the +3 valance state of Sm dopants. Mg K-edge XANES features convey the lesser coordination of Mg2+ ions upon increasing the Sm3+ ions. O K-edge XANES convey the formation of O2- vacancies or F centers upon Sm3+ doping. Two excitation wavelengths, λexcitation = 275 nm, and λexcitation = 405 nm, have shown significant emission at blue and yellow-red regions, respectively. Additionally, utilizing XANES as a methodological tool for examining defects and incorporating PL and TL findings provides a comprehensive understanding that is relatively infrequent in previous research. Thermoluminescence (TL) studies, conducted over a temperature range of 340 K to 675 K with three irradiation doses of γ-rays (100 Gy, 500 Gy, and 1000 Gy) are convincing the formation of multiple levels of radiative traps, enhancing peak intensity at 437 K and radiation doses independent of peak intensity at 437 K.