Browsing by Author "Karsu, EC"

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    Kinetic characterization of MgB4O7:Dy,Na thermoluminescent phosphor
    Karsu, EC; Gökce, M; Ege, A; Karali, T; Can, N; Prokic, M
    Dosimeters of MgB4O7 doped with Dy and Na have many valuable features such as high sensitivity, tissue equivalence, low fading, non-requirement of annealing and insensitivity to light. Thermoluminescence studies of Dy and Na doped MgB4O7 samples showed that a glow emission peaked at about 195 degrees C. In this study, the trapping parameters associated with the main dosimetric peak, namely at 195 degrees C, of Dy and Na doped MgB4O7 are investigated. Isothermal luminescence decay, glow curve shape, initial rise (linear regression) and T-m - T-stop methods were used. We report the results on the kinetic behaviour and activation energy determination of the peak occurring at 195 degrees C with a moderate heating rate of 2 degrees C s(-1). The average activation energies obtained by the isothermal luminescence decay method, glow curve shape method and initial rise method are calculated to be 1.03 eV, 0.95 eV and 0.89 eV, respectively. The methods mentioned above indicate that the dosimetric peak may consist of one or more second-order components. The frequency factors obtained by the three methods are 3.5 x 10(10) s(-1), 1.6 x 10(9) s(-1) and 3.4 x 10(8) s(-1),respectively. Results obtained using all these methods are compared and discussed.
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    Luminescence study of some yttrium tantalate-based phosphors
    Karsu, EC; Popovici, EJ; Ege, A; Morar, M; Indrea, E; Karali, T; Can, N
    Yttrium tantalate (YTaO4), yttrium niobium-tantalate (YTaNbO4), yttrium niobate (YNbO4), europium and terbium activated yttrium tantalate (YTaO4:Eu, YTaO4:Tb) and europium activated yttrium niobate (YNbO4:Eu) phosphors were prepared by solid-state reaction, from a homogeneous mixture consisting of Y2O3, Eu2O3, Tb4O7, Ta2O5, Nb2O5 and Na2SO4 as flux. Photoluminescence (PL), thermally stimulated luminescence (TSL), X-ray diffraction (XRD) and scanning electron microscopy (SEM) of yttrium tantalate based phosphors are reported. In the present study TSL characteristics of these phosphors were first investigated and reported after exposure to beta, UV (311 nm) and X-ray radiations. (C) 2011 Elsevier B.V. All rights reserved.