Browsing by Author "Ayvackl M."

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    Radioluminescence and thermoluminescence of albite at low temperature
    (2011) Can N.; Garcia-Guinea J.; Kibar R.; Etin A.; Ayvackl M.; Townsend P.D.
    Feldspar as an archaeological and geological natural material for dating and retrospective dosimetry is receiving more and more attention because of its useful luminescence properties. In this study, the 25-280 K thermoluminescence (TL) and radioluminescence (RL) spectra in albite, which is a component of the two main feldspar series, the alkali feldspar (Na, K)AlSi3O 8 and the plagioclases (NaAlSi3O8-CaAl 2Si2O8) have been presented for aliquots along (001) and (010) crystallographic orientations. There are four main emission bands that are considered to arise from complexes of intrinsic defects linked in larger complexes with impurities such as Na+, Mn2+ or Fe3+ ions. The consequence of their association is to produce different luminescence efficiencies that produce wavelength sensitive TL curves. Radioluminescence data at low temperature for albites is distorted by contributions from the TL sites, even when the RL is run in a cooling cycle. This indicates the potential for a far more general problem for analysis of low temperature RL in insulating materials. © 2011 Elsevier Ltd. All rights reserved.
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    Photoluminescence investigations of Li 2SiO 3:Ln (Ln=Er 3+, Eu 3+, Dy 3+, Sm 3+) phosphors
    (2012) Sabikoglu I.; Ayvackl M.; Bergeron A.; Ege A.; Can N.
    In this study, we report a comprehensive structural and photoluminescence (PL) study on lithium metasilicate (Li 2SiO 3) phosphor ceramics doped with four rare earth (RE) ions. X-ray diffraction (XRD) patterns show a dominant phase, characteristic of the orthorhombic structure Li 2SiO 3 compound and the presence of dopants has no effect on the basic crystal structure of the material. The first excited state Er 3+ luminescence at 1.54 μm arises from a sharp atomic-like radiative transition between the 4I 13/2 state and the 4I 15/2 state (ground level) under a 532 nm line of an Ar ion laser excitation. Sm doped samples showed Sm 3+ emission characteristics corresponding to the some 4G 5/2→ 6H j (j=5/2,9/2,11/2) transitions indicating a strong crystal-field effect. PL spectra of Eu doped material exhibited peaks corresponding to the 5D 0→ 7F j (j=0,1,2,3 and 4) transitions under 405 nm excitation. The dominant red color emission at 612 nm from the hypersensitive ( 5D 0→ 7F 2) transition of Eu 3+ indicates the inversion antisymmetry crystal field around Eu 3+ ion, which is favorable to improve the red color purity. Dy doped samples showed the Dy 3+ emission characteristic due to the 4F 9/2→ 6H 13/2 transition. Their relative intensity ratios also suggested the presence of a symmetric environment around the metal ion. We suggest that lithium metasilicate has enough potential candidates to be a phosphor material. © 2012 Elsevier B.V.
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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.