Yazar "Oglakci, M." seçeneğine göre listele

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    A study on thermoluminescence behaviour of Eu doped LaB3O6 irradiated with beta particles
    (Pergamon-Elsevier Science Ltd, 2020) Halefoglu, Y. Z.; Oglakci, M.; Portakal, Z. G.; Akca, S.; Souadi, G. O.; Canimoglu, A.; Topaksu, M.
    Lantanium triborate (LaB3O6) samples doped with Eu3+ ions are synthesized via combustion route. This study primarily reports the thermoluminescence (TL) behaviour of LaB3O6 host. X-ray diffraction (XRD) pattern reveals that LaB3O6 exhibits a single phase matched with JCPDS card 98-002-3609. Dose response, reusability and trap parameters of TL glow curves are evaluated to clearly reveal the TL features. The results show that the peak positions of TL glow curves are affected by varying the concentration of Eu. The experimental results obtained from the dose-response of LaB3O6:Eu3+ (1%) which has given high TL intensity reveal that the intensity of TL given by the total area under glow curves shows a good linearity (b = 0.997) up to 20 Gy. In addition, the minimum detectable dose (MDD) value has been calculated as 1.45 mGy with a standard deviation of 0.8%. Main TL peak maxima is observed around 197 degrees C with heating rate (HR) of 2 degrees Cs-1. An anomalous HR effect is observed for this peak in the range of 0.5-20 degrees Cs-1 with beta dose of 5 Gy. To find the overlapping peak numbers and determine the kinetic parameters of the main peak of LaB3O6:Eu3+ (1%), Initial Rise (IR) method using T-m - T-stop experiment and CGCD analysis have been performed for HRs of 0.5 and 2 degrees Cs-1. It can be said that the results of the methods are in good agreement when same trap numbers (at least eight separate peaks for both) and close energy values are taken into consideration. Deconvolution procedure of LaB3O6: Eu3+(1%) is performed using general order kinetic equation by R studio 'tgcd'. Additionally, the lifetimes of each deconvolved peaks by CGCD of Eu activated LaB3O6 (1%) have been calculated. Based on the results it can be put forth that TL characteristics of Eu doped LaB3O6 can be used as a promising material for thermoluminescence dosimetry-environmental applications.
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    Anomalous heating rate response of beta irradiated Sm3+ and Tb3+ doped BaAl2O4 phosphors
    (Elsevier Science Sa, 2018) Kaynar, U. H.; Guvener, E.; Ayvacikli, M.; Dogan, T.; Balci-Yegen, S.; Oglakci, M.; Topaksu, M.
    The stuffed derivative of the tridymite structure, the oxide BaAl2O4 has been regarded as a long persistent phosphor. Thermoluminescence (TL) glow curve peaks of thin pellet samples of undoped and, Sm3+ and Tb3+ doped BaAl2O4 prepared by combustion method was reported. The structure of the compounds was monitored by X-ray diffraction and found a single-phase compound with a hexagonal structure. Performing a series of TL measurements for the temperature range from room temperature to 400 degrees C, the effect of beta radiation dose on TL response, various TL heating rate (HR) properties of undoped and Sm3+ and Tb3+ doped BaAl2O4 phosphors were investigated. Peak shape method was also utilized to assess the trap parameters. The activation energy of the main peak at 128 degrees C was found to be 0.97 eV. TL glow curves obtained from undoped and Tb3+ doped BaAl2O4 decrease with increasing HR value (varying from 0.5 to 15 degrees C s(-1)) in a way matching with thermal quenching effect. Contrary to expectations, anomalous HR dependence was observed on Sm3+ doped BaAl2O4 sample and a semi-localized transition model has been used in order to explain such behaviour. (C) 2018 Elsevier B.V. All rights reserved.
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    Comparison of thermoluminescence characteristics of undoped and europium doped YAl3(BO3)4 phosphor synthesized by combustion method: Anomalous heating rate, dose response and kinetic analyses
    (Pergamon-Elsevier Science Ltd, 2023) Kaynar, Umit H.; Oglakci, M.; Bulcar, K.; Benourdja, S.; Bakr, M.; Ayvacikli, M.; Canimoglu, A.
    In this study, undoped and YAl3(BO3)(4) phosphors doped with Eu3+ at varying concentrations (x = 0.5 to 7 wt%) produced by a combustion process have been thoroughly examined by using the X-ray diffraction (XRD) and thermoluminescence (TL) techniques. The crystallized phosphors were confirmed by XRD analysis, and its crystal structure was examined. XRD analyses of the synthesized phosphor is in accordance with ICSD File No 96-152-6006. TL glow curve of undoped sample produced three glow peaks located at 80 degrees C, 240 degrees C, and 360 degrees C with a heating rate of 2 degrees Cs-1 whilst Eu3+ doped one appears at 90 degrees C, 230 degrees C, and 390 degrees C. The undoped example complied with the theory as expected, namely, as the heating rate increased, the TL glow curve shifted towards lower temperatures and decreased in intensity. However, an anomalous change was observed in the sample with Eu3+ additive. The experimental findings from the dose-response of YAl3(BO3)(4):0.5 wt%Eu3+ demonstrate that the intensity of TL provided by the total area under glow curves has an acceptable linearity (r(2):0.999) up to 100 Gy. The intensity of each maximum on the TL glow curve augments proportionally as the heating rate is augmented. Possible reasons of this behaviour are discussed. Various heating rate (VHR) methods (such as Hoogenstraaten's and Booth-Bohun-Parfianovitch) have also been used to estimate kinetic parameters (e.g., energy and frequency factor), which seem to be in good agreement with each other.
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    Structural and spectroscopic properties of LaAlBO3 doped with Eu3+ ions
    (Pergamon-Elsevier Science Ltd, 2019) Halefoglu, Yusuf Ziya; Oglakci, M.; Yuksel, M.; Canimoglu, A.; Topaksu, M.; Can, N.
    In this study, we performed X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) techniques to examine the structure and morphological observation of the samples and thermoluminescence (TL) experiments to extract the trapping parameters and dosimetric properties of LaAlBO3 phosphors doped with Eu at various doping concentrations. Diffraction patterns of obtained sample were well consistent JCPDS card No 98-009-7945, indicating the formation of pure phase. The TL kinetic parameters were estimated by CGCD software. TL glow curves of LaAlBO3:Eu3+ consist of 12 trap levels and exhibited dominantly first order kinetics. Photoluminescence (PL) emission was observed in the range 400-800 nm for LaAlBO3 phosphor doped with Eu3+. The dominant emission of Eu3+ corresponding to the electric dipole transition D-5(0) -> F-7(2) is located at 616 nm. The sharp emission properties exhibited demonstrate that the LaAlBO3 is a suitable host for rare-earth ion doped phosphor material. It is observed that for the variable concentration of Eu3+ on PL studies, the PL intensity augments with increase in the dopant concentration and the concentration quenching was found after 1 mass% of Eu3+. The PL experimental results reveal that LaAlBO3:Eu3+ phosphor as an red emitting phosphor may be promising luminescence materials for the optoelectronic applications.
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    Structural and temperature-dependent photoluminescence properties of NaBaBO3:Ce3+,Tb3+phosphors synthesized using the combustion
    (Elsevier, 2024) Altowyan, Abeer S.; Oglakci, M.; Topaksu, M.; Ozturk, E.; Hakami, Jabir; Coban, M. B.; Keskin, M. Ozgur
    This study explores the structural and temperature-dependent photoluminescence of Ce3+ and Tb3+ doped NaBaBO3 phosphors, synthesized via combustion. Analysis of their crystal structures confirmed excellent alignment with the standard PDF#98-008-0110. Investigation into both room and lowtemperature photoluminescence revealed that the dopants have a significant effect on emission spectra. Ce3+-doped samples exhibited excitation peaks at 275 nm and 358 nm, leading to a primary emission at 419 nm, with enhanced low-temperature emission suggesting reduced non-radiative processes. Tb3+doped phosphors showed excitation from 250 to 377 nm and emissions from blue to deep red, including strong green emission at 550 nm due to 5D4?7F5 transitions. Optimal doping was found at 1 mol% for Ce3+, while Tb3+ showed increased luminescence up to 3 mol%, with concentration quenching observed beyond these points. The study indicates dipole-dipole interactions dominate Ce3+ concentration quenching, whereas Tb3+ involves both electric dipole and quadrupole interactions. This analysis provides insights into enhancing luminescent efficiency and suggests NaBaBO3:xCe3+,Tb3+ phosphors' potential in advancing white LED technology, highlighting their stable luminescent properties at low temperatures. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
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    Synthesis and photoluminescence characteristics of a novel Eu and Tb doped Li2MoO4 phosphor
    (Pergamon-Elsevier Science Ltd, 2021) Souadi, G.; Kaynar, U. H.; Ayvacikli, M.; Coban, M. B.; Oglakci, M.; Canimoglu, A.; Can, N.
    Li2MoO4:x Eu3+ and Li2MoO4:xTb(3+) phosphors, where x = 0.5, 1, 2, 3, 5 and 7 wt%, were synthesized through a gel-combustion method. The XRD data reveals that Eu3+ and Tb3+ doped Li2MoO4 phosphors exhibit a Rhombohedral structure belonging to the space group R3 which matched well with the standard JCPDS files (No.0120763). We present photoluminescence (PL) spectra from Eu and Tb doped Li2MoO4 under 349 nm Nd:YLF pulses laser excitation over the temperature range of 10-300 K. Undoped Li2MoO4 shows a wide broad band around 600 nm because of the intrinsic PL emission of tetrahedral of MoO42- which was in good agreement with previous findings. Under the excitation of 394 nm, the as-synthesized phosphors exhibited sharp and strong intensity PL emission signals in the red (612 nm, D-5(0) -> F-7(2) transition) and green (544 nm, D-5(4) -> F-7(5) transition), respectively. The critical doping concentration of Eu3+ and Tb3+ ions in the Li2MoO4 were estimated to be 2 wt%. The concentration quenching phenomena were discussed, and the critical distances for energy transfer have also been evaluated by the concentration quenching.
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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, U. H.; Oglakci, M.; Sonsuz, M.; Ayvacikli, M.; Topaksu, M.; Canimoglu, 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.