Browsing by Author "Khatab, A"

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    Absorption and photoluminescence spectroscopy of Er3+-doped SrAl2O4 ceramic phosphors
    Ayvacikli, M; Khatab, A; Ege, A; Sabikoglu, I; Henini, M; Can, N
    A spectroscopic characterization of Er3+-doped SrAl2O4 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 360 K and absorption spectra. PL signals containing five emission bands at 1492, 1529, 1541, 1558, and 1600 nm, respectively, have been observed at room temperature for Er3+ transitions in the near infrared region. The samples exhibit a main luminescence peak at 1.54 mu m, which is assigned to recombination via an intra-4f Er3+ transition. Sharp bands centered at around 378, 488, 521, 651, 980, 1492, and 1538 nm in the absorption spectra can be associated with transitions from I-4(15/2) level to H-2(9/2), F-4(7/2), H-2(11/2), F-4(9/2), I-4(11/2), H-2(11/2), and I-4(13/2) levels, respectively. The sharp emission peaks and excellent luminescence properties show that SrAl2O4 is a suitable host for rare-earth-doped phosphors, which may be suitable for optical applications.
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    Solid state synthesis of SrAl2O4:Mn2+ co-doped with Nd3+ phosphor and its optical properties
    Ayvacikli, M; Kotan, Z; Ekdal, E; Karabulut, Y; Canimoglu, A; Guinea, JG; 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 SrAl2O4 compound. Small amounts of the dopants MnCO3 and Nd2O3 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 I-4(9/2) 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 I-4(9/2) -> (4)G(7/2) and F-4(3/2) -> I-4(J) (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. (C) 2013 Elsevier B.V. All rights reserved.