Sodium-zinc phosphate glasses activated with Dy3+/Tb3+ and Dy3+/Tb3+/Eu3+ for photonic applications

A detailed spectroscopic investigation was carried out on sodium–zinc–phosphate glass matrices activated with Dy 3+ /Tb 3+ and Dy 3+ /Tb 3+ /Eu 3+ ions. The glasses were fabricated using the conventional melt-quenching route and examined through photoluminescence measurements and luminescence decay analysis. Under 349 nm excitation, the co-doped Dy 3+ /Tb 3+ glass exhibits a yellow–green emission characterized by CIE1931 chromaticity coordinates (0.364, 0.558). In this system, Dy 3+ ions act as sensitizers for Tb 3+ emissions associated with the 5 D 4 → 7 F J transitions via a non-radiative energy transfer process. Conversely, back energy transfer/cross relaxation from Tb 3+ ( 5 D 3 ) to Dy 3+ ( 4 F 7/2 )/Dy 3+ ( 6 H 15/2 ) occurs, reaching an efficiency of 48.7%. For the tri-doped glass, the emission color can be tuned by the excitation wavelength. Excitation at 349 nm produces a warm (yellowish–orange) emission with CIE1931 coordinates (0.493, 0.453) and a correlated color temperature (CCT) of 2588 K, whereas excitation at 393 nm results in a reddish–orange emission with coordinates (0.639, 0.347) and a CCT of 2215 K. The (0.639, 0.347) coordinates are close to those (0.67, 0.33) of the red phosphor established by the National Television Standard Committee (NTSC). The luminescence originates mainly from the Tb 3+ ( 5 D 4 → 7 F 5 ), Dy 3+ ( 4 F 9/2 → 6 H 15/2,13/2 ) and Eu 3+ ( 5 D 0 → 7 F 2 ) transitions. Non-radiative energy transfer pathways are identified from Dy 3+ to Tb 3+ /Eu 3+ and from Tb 3+ to Eu 3+ , with efficiencies of 61.7% and 57.4%, respectively. The evaluated results reveal that the novelty of this work lies in the development of a new host doped with Dy 3+ , Tb 3+ and Eu 3+ ions, emerging as a promising color-tunable luminescent material for photonic applications, such as warm-LED and NSTC red display technologies.