Browsing by Author "Khatab A."

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    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.
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    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.
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    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.