Luminescence characteristics of Dy3+ doped sodium alumina borate glass: Role of silver

Abstract

Metallic nanoparticle (NP) doped glasses have been studied as promising candidates for various technological applications due to their ability to improve the luminescence properties of rare earth ions. In this work, Dy2O3 and Ag2O co-doped sodium alumina borate glasses were synthesized by conventional melt-quenching technique. Raman analysis verified the existence of [BO3] and [BO4] groups with B–O stretching vibrations in the prepared glasses. Transmission electron microscope images confirmed the presence of spherical Ag NPs, whose average diameter is about 7.60 nm, in H-0.5Dy1Ag glass matrix. The optical and luminescence properties were investigated according to Ag concentrations. The negative value of the bonding parameters, calculated from the absorption spectra, indicates the ionic nature between the Dy3+ ions and its surrounding ligands. In order to determine the nature of the Dy-O bond and the symmetry around the Dy3+ ion environment, Judd–Ofelt intensity parameters (Ω λ, λ = 2, 4, 6) were obtained from the absorption spectra. The luminescence spectra obtained under 350 nm excitation exhibits four emission bands at 481 (4F9/2→6H15/2), 572 (4F9/2→6H13/2), 662 (4F9/2→6H11/2), and 750 (4F9/2→6H9/2) nm. The intensity of emission spectra increases with Ag2O content until 1.0 wt% in H-0.5Dy-yAg glasses and then decreases due to the back-energy transfer (ET) from Dy3+ to Ag+. The ET mechanism from Ag+ to Dy3+ ion for H-1Ag-xDy glasses were investigated through Forster-Dexter’s theory and were found to be quadrupole-quadrupole type. The various radiative properties were calculated by using Judd-Ofelt intensity parameters and emission spectra. It was found that the 572 nm emission band, located in the yellow region, has higher radiative parameters. As a function of Ag concentration, the Y/B values, Commission Internationale d’Eclairage (CIE) chromaticity coordinates (x,y) and correlated color temperatures (CCT) were evaluated. The CIE chromaticity coordinates and CCT values of all glasses are located in the white light region. The decay time values of 1S0→3D1 transition of Ag+ ions and 4F9/2→6H13/2 transition of Dy3+ ions confirm the ET from Ag+ to Dy3+ ions. Overall, the present study indicates that the synthesized glasses with Ag addition exhibits improved luminescence, making them potential candidate for white LEDs.