Browsing by Author "Henini M."
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Item Absorption and photoluminescence spectroscopy of Er 3+-doped SrAl 2O 4 ceramic phosphors(2012) Ayvackl M.; Khatab A.; Ege A.; Şabikoǧlu I.; Henini M.; Can N.A spectroscopic characterization of Er 3+-doped SrAl 2O 4 phosphor materials synthesized by a solid-state reaction method with Er concentrations varying from 0.1 to 1 mol% has been performed by studying photoluminescence (PL) in the temperature range 10 to 360K and absorption spectra. PL signals containing five emission bands at 1492, 1529, 1541, 1558, and 1600nm, respectively, have been observed at room temperature for Er 3+ transitions in the near infrared region. The samples exhibit a main luminescence peak at 1.54 μm, which is assigned to recombination via an intra-4f Er 3+ transition. Sharp bands centered at around 378, 488, 521, 651, 980, 1492, and 1538nm in the absorption spectra can be associated with transitions from 4I 15/2 level to 2H 9/2, 4F 7/2, 2H 11/2, 4F 9/2, 4I 11/2, 2H 11/2, and 4I 13/2 levels, respectively. The sharp emission peaks and excellent luminescence properties show that SrAl 2O 4 is a suitable host for rare-earth-doped phosphors, which may be suitable for optical applications. © 2012 Taylor & Francis.Item Luminescence characterization of cerium doped yttrium gadolinium aluminate phosphors(Elsevier B.V., 2012) Uysal Satilmis S.; Ege A.; Ayvacikli M.; Khatab A.; Ekdal E.; Popovici E.J.; Henini M.; Can N.Yttrium gadolinium aluminate ((Y1-xGdx) 3Al5O12:Ce) doped cerium phosphors with the different yttrium and gadolinium concentration were prepared by a wet-chemical route via the reagent simultaneous addition technique (WCS-SimAdd). The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL), radioluminescence (RL) of cerium doped yttrium gadolinium aluminate phosphors. With increasing Gd dopant concentration, the PL intensity was shifted to the red region. Preliminary RL measurements were performed to further evaluate these newly prepared materials. Intense RL was observed that is typical of Ce3+ doped structure. © 2012 Elsevier B.V. All rights reserved.Item Solid state synthesis of SrAl2O4:Mn2+ co-doped with Nd3+ phosphor and its optical properties(2013) Ayvacikli M.; Kotan Z.; Ekdal E.; Karabulut Y.; Canimoglu A.; Garcia Guinea J.; Khatab A.; Henini M.; Can N.The optical properties of alkaline earth aluminates doped with rare earth ions have received much attention in the last years and this is due to their chemical stability, long-afterglow (LAG) phosphorescence and high quantum efficiency. However, there is a lack of understanding about the nature of the rare earth ion trapping sites and the mechanisms which could activate and improve the emission centers in these materials. Therefore a new phosphor material composition, SrAl2O4:Mn2+, co-doped with Nd3+ was synthesized by a traditional solid-state reaction method. The influence of transition metal and rare earth doping on crystal structure and its luminescence properties have been investigated by using X-ray diffraction (XRD), Raman scattering, Photoluminescence (PL) and Radioluminescence (RL). Analysis of the related diffraction patterns has revealed a major phase characteristic of the monoclinic SrAl2O 4 compound. Small amounts of the dopants MnCO3 and Nd 2O3 have almost no effect on the crsytalline phase composition. Characteristic absorption bands from Nd3+ 4f-4f transitions in the spectra can be assigned to the transitions from the ground state 4I9/2 to the excited states. The luminescence of Mn2+ activated SrAl2O4 exhibits a broad green emission band from the synthesized phosphor particles under different excitation sources. This corresponds to the spin-forbidden transition of the d-orbital electron associated with the Mn2+ ion. In photo- and radio-luminescence spectra, Nd3+ 4f-4f transition peaks were observed. The emitted radiations for different luminescence techniques were dominated by 560, 870, 1057 and 1335 nm peaks in the visible and NIR regions as a result of 4I9/2→4G7/2 and 4F3/2→4IJ (J=9/2, 11/2 and 13/2) transitions of Nd3+ ions, respectively. Multiple emission lines observed at each of these techniques are due to the crystal field splitting of the ground state of the emitting ions. The nature of the emission lines is discussed. © 2013 Elsevier B.V.Item Radioluminescence and photoluminescence characterization of Eu and Tb doped barium stannate phosphor ceramics(2014) Ayvacikli M.; Canimoglu A.; Karabulut Y.; Kotan Z.; Herval L.K.S.; De Godoy M.P.F.; Galvão Gobato Y.; Henini M.; Can N.In this paper, we report on structural and optical properties of terbium and europium doped barium stannate phosphors (BaSnO3) synthesised by conventional solid state reaction method. We have studied those materials by using X-ray diffraction (XRD), radioluminescence (RL) and photoluminescence (PL) techniques. XRD patterns confirm that the BaSnO3 sintered at 1400 C exhibit orthorhombic structure and that the Tb3+ and Eu3+ substitution of Ba2+ does not change the structure of the BaSnO 3 host. The optical emission spectrum is characterized a broad band centered at 897 nm (1.38 eV), with a high-energy tail approximately 750 nm from the host lattice. Other emission signals that are characteristic of the 3 + oxidation state of rare earth elements were generated by Eu and Tb doping. Luminescence measurements show that the series of emission states 5D4 → 7F6, 5D 4 → 7F5, 5D4 → 7F4 and 5D4 → 7F3 corresponding to the typical 4f → 4f infra-configuration forbidden transitions of Tb3+ are appeared and the major emission peak at 540 nm is due to 5D4 → 7F5 transitions of Tb3+. On the other hand, the emission spectrum of Eu doped BaSnO3 phosphor exhibits a series of emission bands, which are attributed to the 5D0 → 7Fj (j = 0-4) transitions of Eu3+ ions. The dominant emission of Eu3+ corresponding to the electric dipole transition 5D0 → 7F2 is located at 613 nm. The sharp emission properties exhibited demonstrate that the BaSnO3 is a suitable host for rare-earth ion doped phosphor material. This work clearly confirms the unusual near infrared (NIR) PL discovered by H. Mizoguchi et al. in BaSnO3 at room temperature. © 2014 Elsevier B.V. All rights reserved.Item Visible to infrared low temperature luminescence of Er3+, Nd3+ and Sm3+ in CaSnO3 phosphors(Elsevier Ltd, 2015) Orsi Gordo V.; Tuncer Arslanli Y.; Canimoglu A.; Ayvacikli M.; Galvão Gobato Y.; Henini M.; Can N.Novel stannate phosphor, orthorhombic CaSnO3 phosphors doped with Er3+, Nd3+ and Sm3+ have been synthesized by a conventional solid-state method under N2+H2 gas flow. Visible and near-infrared photoluminescence (PL) properties were investigated as function of laser power and temperature. It was observed that all dopant ions are well incorporated in CaSnO3 and are responsible for the optical emission in the temperature range of 10-300K. PL peaks at 490, 546, 656, 696, 894, 1065, and 1344nm were observed for the CaSnO3:Nd3+ phosphor and associated to f-f transition of Nd3+ ion. Emissions at 564, 600-607, 646-656 and 714nm were detected for the CaSnO3:Sm3+. The strongest one, observed at 600nm, was associated to 4G5/2→6H7/2 of Sm3. Emission lines at 528, 548, 662 at 852nm were also seen for CaSnO3:Er3+ and correspond to Er3+ intra-4fn shell transitions. In addition, at low temperatures, a stark splitting of the 4f electron energy levels of the Er3+ ions were observed in infrared region (1520-1558nm) and assigned to the transition between the 4I13/2 state and the 4I15/2 state. Finally, our results show that the rare earth doped CaSnO3 has remarkable potential for applications as optical material since it exhibits efficient and sharp emissions due to rare earth ions. © 2015 Elsevier Ltd.Item Enhancement of the luminescence intensity by co-doping Mn2+ into Er3+-doped SrAl2O4(Elsevier, 2015) De Herval L.K.S.; Tuncer Arslanlar Y.; Ayvacikli M.; Iikawa F.; Nobrega J.A.; Pizani P.S.; Galvão Gobato Y.; Can N.; Henini M.; De Godoy M.P.F.Structural and optical properties of erbium- and manganese-doped strontium aluminates (SrAl2O4) phosphor materials synthesized by a solid state reaction were investigated. The samples presented the fundamental optical transitions due to Er3+ and Mn2+ which are typical features of the well-diluted doping process. A significant enhancement of the Er3+ optical emission band at 1530 nm was observed when the matrix is co-doped with Mn. Photoluminescence intensity under ultraviolet excitation was three times larger as compared to samples without Mn content. A model of energy transfer mechanism from Mn2+ to Er3+ ions due to optical energy matching is proposed to explain the experimental results. This result, presented first time, can be applied as useful tool for developments in optical communications. © 2015 Elsevier B.V. All rights reserved.