Yazar "Souadi, G." seçeneğine göre listele

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    Anomalous dose behaviour of thermoluminescence glow curves and kinetic analysis of beta irradiated YAl3(BO3)4:Tb phosphor
    (Pergamon-Elsevier Science Ltd, 2023) Souadi, G.; Bulcar, K.; Kaynar, Umit H.; Ayvacikli, M.; Topaksu, M.; Cam-Kaynar, S.; Can, N.
    With the aid of thermoluminescence (TL), we have extensively studied YAl3(BO3)4 host matrices incorporated with Tb3+ at different doping contents, which have been produced by combustion. The measured the TL glow curves exposed to beta rays at different doses consisted of four broad peaks located at around 76, 126, 230, and 378 degrees C. The peak maximum of the 230 degrees C TL peak shifts toward higher temperatures after 5 Gy beta irradiation while the other peak maxima almost remain constant. It is peculiar that 230 degrees C peak maximum shifts to higher temperatures with increased radiation dose and can be attributed to the multiple phases of the sample. A TL glow curve exhibits a proportional increase in intensity with increased the heating rate. A discussion of the possible causes of this pattern is provided. Observed peaks using the TmTstop method are due to the presence of a quasicontinuous distribution of traps. The parameters of the traps have also been estimated using various heating rate methods in excellent agreement with one another.
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    Luminescence of undoped and Eu3+activated zinc gallate phosphor: Synthesis, unusual intense 5D0 ? 7F4 red emission
    (Pergamon-Elsevier Science Ltd, 2023) Souadi, G.; Kaynar, Umit H.; Ayvacikli, M.; Can, N.
    A series of Eu3+-doped ZnGa2O4 samples were synthesized via the urea-glycine combustion route. Powder X-ray diffraction (XRD) was used to investigate the crystallinity of the samples, energy dispersive spectroscopy (EDS) to explore the elemental composition, Fourier transform infrared (FTIR), to observe the vibrational modes of the samples, photoluminescence (PL) to determine the luminescence properties. The XRD data prove that the samples remain single cubic structure even at high concentrations of Eu3+, enabling the formation of a unique emission spectrum. The active ion concentration was varied to examine the influence of concentration on luminescent properties. This study revealed a 5D0 & RARR;7F4 transition located at 700 nm with unusual intensity that has not been documented in the literature, which suggests that the active ion concentration can influence the luminescent characteristics of the phosphors. The increasing Eu3+ content increases the number of Eu3+ ions in ZnGa2O4 host lattice, which enhances the luminescence efficiency of the phosphor. However, beyond a certain level of Eu3+content (i.e., 3 wt% Eu3+), the number of Eu3+ ions becomes excessive, resulting in a reduction in luminescence efficiency due to concentration quenching. The dipole dipole interaction is elucidated to play a prominent role in the mechanism of Eu3+ quenching in the ZnGa2O4. An assessment of color coordinates based on emission spectra reveals that the coordinates shift from blue to the white light region, and then to red as Eu3+ content increases. This suggests that there is a substantial relationship between the Eu3+ concentration and the measured color coordinates.
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    Synthesis, characterization and enhanced photoluminescence and temperature dependence of ZrO2:Dy3+phosphors upon incorporation of K plus ions
    (Elsevier Sci Ltd, 2023) Can, N.; Coban, M. B.; Souadi, G.; Kaynar, Umit H.; Ayvacikli, M.; Guinea, J. Garcia; Karali, E. Ekdal
    This study reports the successful synthesis and comprehensive characterization of ZrO2:Dy3+ phosphors with the incorporation of K+ ions. The introduction of Dy3+ and K+ in the ZrO2 lattice as lanthanide activators demonstrates its potential as an efficient host material. The structural integrity of ZrO2 remains unaltered following the doping process. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the presence of Zr-O and O-H stretching, along with H2O bending modes in the phosphor sample. The wide luminescence band seen at 460 nm is attributed to luminescence defects in the ZrO2 induced by oxygen, and the presence of water molecules. Photoluminescence (PL) spectra analysis reveals pronounced emission peaks at 491 and 578 nm, corresponding to 4F9/2 -> 6H15/2 and 4F9/2 -> 6H13/2 transitions, respectively, upon excitation at 349 nm. Optimizing the Dy3+ doping concentration to 0.4 wt% and achieving a critical distance of 31.82 angstrom resulted in efficient energy transfer. Notably, co-doping K+ as a charge compensator significantly enhances the luminescence intensity. Moreover, at lower temperatures, direct excitation of Dy3+ ions through our pump wavelength, coupled with exciton-mediated energy transfer, leads to a remarkable increase in PL intensity. Tailoring the doping concentrations effectively shifts the emission spectrum of the phosphor mixture, aligning with the standard white light illumination co-ordinates (0.333, 0.333). This property positions the material as a promising candidate for applications in white light-emitting diodes (WLEDs) and various high-quality lighting applications. The enhanced photoluminescence and temperature dependence observed in ZrO2:Dy3+ phosphors upon the incorporation of K+ ions pave the way for their potential utilization in advanced luminescent devices.
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    Thermoluminescence characteristics of a novel Li2MoO4 phosphor: Heating rate, dose response and kinetic parameters
    (Pergamon-Elsevier Science Ltd, 2022) Souadi, G.; Kaynar, Ümit. Hüseyin; Oğlakçı, M.; Sonsuz, M.; Ayvacıklı, M.; Topaksu, M.; Canımoğlu, A.
    Lithium molybdate (Li2MoO4) phosphor was synthesized by a gel combustion method and its thermoluminescence properties were studied with the irradiation of beta. Various Heating Rate (VHR), Initial Rise (IR), and Computerized Glow Curve Deconvolution (CGCD) methods were used to determine the kinetic parameters (activation energy E (eV), frequency factor s (s(-1)), and kinetic order b) of the visible glow peaks. According to the kinetic study, the TL glow curve is made up of seven separate peaks with activation energies of 1.05, 0.76, 0.40, 0.60, 0.78, 1.81 and 1.25 eV and these peaks follow general-order kinetics. The results clearly showed that undoped Li2MoO4 has a potential to be considered in dosimetric applications where high doses have to be monitored as in the case of clinical dosimetry.
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    Thermoluminescence glow curve analysis and kinetic parameters of Eu doped Li2MoO4 ceramic phosphors
    (Elsevier Sci Ltd, 2022) Souadi, G.; Oğlakçı, M.; Kaynar, Ümit Hüseyin; Correcher, V.; Benavente, J. F.; Bulcar, K.; Ayvacıklı, M.
    LiMoO4: x Eu ceramic phosphors with x = 0.5, 1, 2, 3, 5, and 7 mol% were synthesized using a gel combustion method. X-ray diffraction (XRD) measurements confirmed a rhombohedral structure (space group R-3) of synthesized compounds. Following irradiation with 50 Gy beta dose, the sample doped with 5 mol% Eu exhibited the highest integrated thermoluminescence (TL) intensity. In order to evaluate dose-response, samples were irradiated with beta radiation for 10-1000 Gy. TL intensity with 1000 Gy dose without saturation yielded the highest integrated value. Different methods were employed to determine the number of peaks, the trap structure, and the kinetic parameters of the thermoluminescence glow curve of Eu doped Li2MoO4: the Hoogenstraaten method, the Booth-Bohun-Parfianovitch method, the initial rise method (IR), combined with the T-M-T-stop experiment, various heating rates (VHR), and glow curve fitting with two different software packages. Based on the glow curve deconvolution obtained using both software packages, the component TL glow peaks present in the complex glow curve are composed of well-isolated nine overlapping glow peaks. Two software packages have shown quite similar activation energies and frequency factors.
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    Unravelling the impact of unusual heating rate, dose-response and trap parameters on the thermoluminescence of Sm3+activated GdAl3(BO3)4 phosphors exposed to beta particle irradiation
    (Pergamon-Elsevier Science Ltd, 2023) Souadi, G.; Kaynar, Umit H.; Sonsuz, M.; Akca-Ozalp, S.; Ayvacikli, M.; Topaksu, M.; Ozmen, O. T.
    The thermoluminescence of GdAl3(BO3)4 (GAB) doped with various concentrations of Sm3+ (i.e. from 0.5 to 7 wt %), prepared by gel combustion, was studied. TL glow peaks at 78 degrees C and 225 degrees C are observed. The intensity of the glow peak at 225 degrees C increased with a faster heating rate. To gain insight into the trap activation energies, the methods of Hoogenstraaten and Booth-Bohun-Parfianovitch were used, where the calculated activation energies are 0.57 eV and 0.60 eV for Peak I and 1.69 eV and 1.71 eV for Peak II respectively. The dose-response of GAB:0.5 wt%Sm3+ demonstrates robust linearity up to 40 Gy, with a strong correlation coefficient of 0.999. Both TM-Tstop combined with the Initial Rise (IR) and Computerized Glow Curve Deconvolution (CGCD) techniques were employed, which revealed six overlapping glow peaks beneath the main peaks. Additionally, the results suggest that the TL signal can be efficiently exploited for radiation dosimetry applications.