Lithium-aluminum-zinc phosphate glasses activated with Sm3+, Sm3+/Eu3+ and Sm3+/Tb3+ for reddish-orange and white light generation

Spectroscopic evaluation of Sm3+, Sm3+/Eu3+ and Sm3+/Tb3+ doped lithium-aluminum-zinc phosphate glasses, based on excitation and emission spectra, and emission decay time measurements, were particularly focused on reddish-orange and white light emitting diode applications. The Sm3+ doped glass exhibits a reddish-orange emission tonality of 1676 K and a high color purity (CP) of 97.6% upon 408 nm excitation. The Sm3+/Eu3+ co-doped glass displays reddish-orange emission tonality of 1621 K (CP = 98.0%) and 2012 K (CP = 98.7%), upon 346 and 392 nm excitations, respectively. The Sm3+/Tb3+ co-doped glass emits neutral white light of 4946 and 4301 K upon 337 and 377 nm excitations, respectively, as well warm white light of 3504 K and reddish-orange light of 1758 K (CP = 91.5%) upon 370 and 396 nm excitations, respectively. The Sm3+/Tb3+ co-doped glass, excited at 337 and 396 nm, shows the highest values of luminous efficiency of radiation (LER = 444 lm/W) and color rendering index (CRI = 97), respectively. The Tb3+ and Sm3+ emission decay shortening in presence of Sm3+ and Eu3+, respectively, points out to Tb3+ -> Sm3+ and Sm3+ -> Eu3+ non-radiative energy transfers, with efficiencies of 8% and 21%, respectively. The Inokuti-Hirayama model suggests that such energy transfer processes might be dominated by an electric dipole-dipole interaction inside Tb3+-Sm3+ and Sm3+-Eu3+ clusters. (C) 2020 Elsevier B.V. All rights reserved.