title: Structural and photoluminescence properties of Eu(3+) doped α-Ag2WO4 synthesized by the green coprecipitation methodology.
abstract: Europium doped silver tungstates α-Ag2-3xEuxWO4 (x = 0, 0.0025, 0.005, 0.0075 and 0.01 mol) were synthesized by the coprecipitation method at 90 °C for 30 minutes. These crystals were structurally characterized by means of X-ray diffraction (XRD), Rietveld refinement, and micro-Raman (MR) and Fourier transformed infrared (FT-IR) spectroscopies. Field emission scanning electron microscopy (FE-SEM) images were employed to observe the shape of the crystals. The optical properties were investigated by ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) measurements. The XRD pattern indicated structural organization at a long range for all undoped and Eu-doped samples, while MR and FT-IR revealed that the presence of the Eu(3+) ions favors the structural organization at a short range. The Rietveld refinement showed that all the crystals are monophasic with an orthorhombic structure and the Pn2[combining macron]n space group. The refined lattice parameters and atomic positions were employed to model the WO6 and AgOn (n = 2, 4, 6 and 7) polyhedra in the unit cell. FE-SEM analysis revealed nanorod-like microcrystals with growth of metallic silver on the surface. Further, the UV-vis absorption spectra indicated the existence of intermediary energy levels within the band gap. PL spectra showed a broad band related to the [WO6] group and characteristic narrow peaks due to the f-f transitions of Eu(3+) as a result of efficient energy transfer from the matrix. Also, the emission line shape transitions from (5)D0 to (7)FJ (J = 0-4) levels of the Eu(3+) were noticed. Among the samples, the most intense photoluminescence results were observed for the α-Ag2-3xEuxWO4 (x = 0.0075) sample. Lifetime decays support that the Eu(3+) ions occupy at least two crystallographic sites. CIE coordinates confirmed the colors of the emission spectra which classify this material as a potential phosphor in the visible range.
authors.affiliation: INCTMN, LIEC, Chemistry Department of the Federal University of São Carlos, P.O. Box 676, 13565-905, São Carlos, SP, Brazil. ilvrosa@ufscar.br.
authors.forename: Ivo M
authors.initials: IM
authors.lastname: Pinatti
authors.forename: Içamira C
authors.initials: IC
authors.lastname: Nogueira
authors.forename: Wyllamanney S
authors.initials: WS
authors.lastname: Pereira
authors.forename: Paula F S
authors.initials: PF
authors.lastname: Pereira
authors.forename: Rosana F
authors.initials: RF
authors.lastname: Gonçalves
authors.forename: José A
authors.initials: JA
authors.lastname: Varela
authors.forename: Elson
authors.initials: E
authors.lastname: Longo
authors.forename: Ieda L V
authors.initials: IL
authors.lastname: Rosa