Luminescence characteristic of RE (RE = Pr, Sm, Eu, Tb, Dy) and energy levels of lanthanide ions in Gd5Si3O12N

Abstract

Polycrystalline Gd5Si3O12N: RE (RE - Pr, Sm, Eu, Tb and Dy) phosphors have been synthesized via a solid-state reaction method at high temperature, and their photoluminescence properties were studied. The absorption peak at about 230 nm is attributed to the host absorption. For the Pr3+-doped sample, the typical excitation lines located at 273 nm originating from the S-8(7/2) -> I-J = 5/2, 7/2) transitions of the Gd3+ ions were observed in the excitation spectra. Upon excitation at 227 nm UV light, the 4f(1)5d -> 4f(2) emission band (350-450 nm) and typical 4f(2) -> 4f(2) emission lines (450-700 nm) assigned to Pr3+ were observed. The Sm3+-doped sample exhibits a bright red emission owing to the (4)G(5/2) -> H-6(J) Q = 5/2, 7/2 and 9/2) transitions. However, the charge transfer band of Sm3+ was not observed in the excitation spectrum. There is a broad band from 200 to 350 nm originating from the charge transfer transition (CT) of the Eu3+ (O2-/N3- -> Eu3+) in the excitation spectra, and the strongest peak in the emission spectra located at 615 nm is due to the electric-dipole D-5(0) -> E-7(2) transition of Eu3+. For the Tb3+-doped sample, it shows D-5(3) -> F-7(J) (J = 5, 4, 3, 2) blue line emissions and D-5(4) -> F-2(J). (J= 6, 5, 4, 3) green line emissions under the excitation of Th3+. The Dy3+-activated sample upon excitation at 349 and 386 nm UV light shows blue-green and orange-red emission lines originating from F-4(9/2) -> H-6(J) 0 = 15/2, 13/2) transitions. In addition, the energy transfer from the host lattice to the luminescence activators (i.e. Pr3+, Sm3+, Eu3+, Tb3+, Dy3+) has been confirmed. In addition, the energy level diagram including the 4f and 5d energy levels of all Ln(2+) and Ln(3+) ions relative to the valence and conduction band of Gd5Si3O12N were constructed and discussed. (C) 2017 Elsevier Masson SAS. All rights reserved.