Electronic Structure, Photoluminescence and Thermoluminescence Studies of Cu-Doped Mg 2 B 2 O 5 Nanophosphors

We synthesized Cu-doped Mg 2 B 2 O 5 nanophosphors using a combustion method, and investigated their structural, morphological, optical band gap, electronic structure, and photo/thermo-luminescence properties using x-ray diffraction (XRD), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HR-TEM), diffuse reflectance spectroscopy (DRS), x-ray absorption near-edge structure (XANES) spectroscopy, photoluminescence (PL) spectroscopy, and thermoluminescence (TL) glow curves. Rietveld refinements of the XRD patterns confirmed the formation of single triclinic phase (space group P-1) for the pure and doped Mg 2 B 2 O 5 nanophosphors. Variations in the cell parameters as a function of dopant concentrations has been determined. The HR-TEM images confirmed the formation of aggregated particles of unusual morphology. The SAED pattern also confirmed the triclinic phase in Cu-doped Mg 2 B 2 O 5 nanophosphors. The band gap of the Cu-doped samples decreased from 5.18 eV to 5.10 eV. The XANES study at the Cu L-edge confirmed the Cu 2+ ions in the Cu-doped Mg 2 B 2 O 5 nanophosphors. The O K-edge spectrum of pure Mg 2 B 2 O 5 confirmed the existence of marginal oxygen vacancies in the sample, which increases after Cu incorporation in the Mg 2 B 2 O 5 nanophosphors. Peak position variation in the O K-edge confirmed the modified hybridization among the O 1 s to O 2 p transitions. From the PL studies and CIE chromaticity diagram, a yellow-reddish color emission from the Cu-doped Mg 2 B 2 O 5 was observed. The TL glow curves obtained after gamma irradiation of the samples were used to evaluate the order of kinetics, activation energy, and frequency factor. The present results infer that Cu-doped magnesium pyroborate could be a potential candidate for solid-state lighting and radiation dosimetry-based applications. Graphical Abstract