Dual-channel enhanced luminescence of double perovskite NaGdMgWO6:Eu3+ phosphor based on alternative excitation and delayed quenching

Series of Eu3+ substituted Na(Gd1 xEux)MgWO6 phosphors were successfully synthesized by a EDTA-citric acid complexing method. The crystal structure, doping site, morphology, and luminescent properties under different Eu3+ concentrations were investigated by XRD, Rietveld refinement, Raman spectra, FTIR, SEM and fluorescence spectra as well as Judd-Ofelt analysis and quenching theory. The phosphors had monoclinic double perovskite structure with space group C2/m, rock-salt ordering of B-site (Mg/W) and layered ordering of A-site (Na/Gd/Eu). The redshift of Raman T-2g(1) mode proved Eu3+ ions had uniformly substituted into A-site. The rare alternative excitation appeared in phosphors that the charge transfer band (CTB) altered from O-W into O-Eu and the strongest excitation altered from CTB into f-f transition of Eu3+. The quenching concentration for hypersensitive D-5(0)-F-7(2) transition of Eu3+ reached up to 50.0 mol%, while both the intensity ratio of D-5(0)-F-7(2)/D-5(0)-F-7(1) and Judd-Ofelt parameter Omega(2) reached the maximum. These two channels of alternative excitation and delayed concentration quenching dually enhanced the luminescence of NaGdMgWO6:Eu3+ phosphor. It is a potential red material for NUV and blue LED chips. (C) 2015 Elsevier B.V. All rights reserved.