Yazar "Alajlani, Y." seçeneğine göre listele

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    Anomalous heating rate and kinetic analysis in the thermoluminescence of GdCa4O(BO3)3
    (Pergamon-Elsevier Science Ltd, 2025) Alajlani, Y.; Oglakci, M.; Barad, A.; Kaynar, U. H.; Topaksu, M.; Canimoglu, A.; Can, N.
    This study investigates the thermoluminescence (TL) properties of GdCa4O(BO3)3 phosphors under beta irradiation, highlighting their potential for dosimetric applications. A prominent glow peak at 175 degrees C was observed, demonstrating consistent sensitivity under preheating conditions. TL glow peaks were studied using variable heating rate (VHR), Tm-Tstop, initial rise (IR), and computerized glow curve deconvolution (CGCD) methods. Eight distinct trap levels with activation energies ranging from 0.92 to 1.28 eV were identified, confirming the material's diverse trap-depth distribution. The dose-response behavior exhibited superlinear characteristics, with a minimum detectable dose (MDD) of 74.4 mGy, making it suitable for low-dose monitoring. Observed anomalous heating rate effects were explained using the semi-localized transition (SLT) model. These findings position GdCa4O(BO3)3 as a promising candidate for luminescence-based technologies.
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    Enhancing the blue luminescence behaviour of the Li co -doped novel phosphor ZnB 2 O 4: Tm 3+
    (Elsevier Science Sa, 2020) Kücük, N.; Kaynar, Ümit H.; Akça, S.; Alajlani, Y.; Yin, L.; Wang, Y.; Can, N.
    [No Abstract Available]
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    Novel Dy incorporated Ca3Y2B4O12 phosphor: Insights into the structure, broadband emission, photoluminescence and cathodoluminescence characteristics
    (Pergamon-Elsevier Science Ltd, 2022) Qaisi, Aziza H.; Kaynar, U. H.; Ayvacikli, M.; Garcia-Guinea, J.; Alajlani, Y.; Topaksu, M.; Can, N.
    This study reports cathodoluminescence (CL) and photoluminescence (PL) properties of undoped borate Ca3Y2B4O12 and Ca3Y2B4O12:x Dy3+ (x = 0.5, 1, 2, 3, 5, and 7) synthesized by gel combustion method. Micro-X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), CL and PL under electron beam and 359 nm pulse laser excitation, respectively were used to investigate characterization and luminescence studies of synthesized samples in the visible wavelength. As-prepared samples match the standard Ca3Y2BO4 phase that belongs to the orthorhombic system with space group Pnma (62) based on XRD results. Under electron beam excitation, this borate host shows a broad band emission from about 250 to 450 nm, peaked at 370 nm which is attributed to NBHOC. All as-prepared phosphors exhibited the characteristic PL and CL emissions of Dy3+ ions corresponding to F-4(9/2)-> H-6(J) transitions when excited with laser at 359 nm. The CL emission spectra of phosphors were identical to those of the PL spectra. Concentration quenching occurred when the doping concentration was 1 mol% in both the CL and PL spectra. The underlying reason for the concentration quenching phenomena observed in the discrete orange-yellow emission peaked at 574 nm of Dy3+ ion-doped Ca3Y2B4O12 phosphor is also discussed. According to these data, we can infer that this new borate can be used as a yellow emitting phosphor in solid-state illumination.
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    Structural and temperature dependence luminescence characteristics of RE (RE=Eu3+, Dy3+, Sm3+and Tb3+) in the new gadolinium aluminate borate phosphor
    (Elsevier Sci Ltd, 2023) Madkhali, O.; Kaynar, Umit H.; Alajlani, Y.; Coban, M. B.; Guinea, J. Garcia; Ayvacikli, M.; Pierson, J. F.
    GdAl3(BO3)4:Dy3+, Sm3+, Eu3+, and Tb3+ samples were successfully achieved via a sol-gel combustion method. The observed XRD analysis confirms the formation of the desired GAB host, indicating rhombohedral structures that agree well with JPCD card number 72-1985. The FTIR analyses show the detection of B -O stretching and B -O -B bending modes as well as Al -O and Gd -O bonds in the phosphor samples. Energy dispersive spectroscopy (EDS) analysis reveals that Sm, Eu, Dy, and Tb have been successfully doped into GdAl3(BO3)4. The observed broad intrinsic luminescence band can be caused by oxygen-induced luminescence defects in the GAB host with hydrous precursors. The luminescence properties of rare earth ion-doped GdAl3(BO3)4 samples are analysed by photoluminescence spectra, showing their optimal doping concentrations and critical distances of Dy3+, Eu3+, Sm3+ and Tb3+ are 2 wt% -25.8 angstrom, 7 wt% -17 angstrom, 1 wt% -32.59 angstrom, and 7 wt% -17.03 angstrom. Additionally, the energy transfer mechanism for luminescence quenching was determined as dipole-dipole (for Dy3+, Eu3+, and Tb3+) or dipole-quadrupole (for Sm3+) and the cross-relaxation process. GdAl3(BO3)4 samples obtained by doping with different RE3+ ions exhibit intense light emissions with different colors originating from different RE3+ ions under 349 nm excitation. When doped with different concentrations of RE3+ ions, the luminescence properties of the samples changed. The synthesized luminescence materials have potential ap-plications in lighting and display technologies.
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    Structural and thermal insights into the luminescent behavior of Dy3+-Doped BaZrO3 with alkali metal codopants under UV radiation
    (Pergamon-Elsevier Science Ltd, 2025) Arslanlar, Y. Tuncer; Alajlani, Y.; Coban, M. B.; Kaynar, U. H.; Aydin, H.; Orucu, H.; Guinea, J. Garcia
    This study investigates the structural, thermal, and photoluminescent properties of Dy3+-doped BaZrO3 (BZO) perovskites, synthesized via a co-precipitation method, incorporating alkali metal codopants (Li+, Na+, and K+). Xray diffraction (XRD) analysis confirmed the retention of the cubic perovskite phase following doping, with Rietveld refinement further revealing minor lattice distortions due to Dy3+incorporation. The Williamson-Hall (W-H) analysis revealed average crystallite sizes of 53 nm and 66 nm for undoped and 0.01 Dy3+-doped BaZrO3, respectively, with corresponding micro-strain values of 1.79 x 10-3 and 1.81 x 10-3, suggesting lattice distortions due to incorporation of Dy3+. Fourier transform infrared (FTIR) spectroscopy confirmed the cubic perovskite structure and subtle structural modifications upon doping. Notably, the absence of moisture-related peaks highlights the effectiveness of the synthesis process, including rigorous drying and calcination steps that prevented hydrous species. Photoluminescence (PL) analysis of Dy3+-doped BaZrO3 exhibited three prominent emission peaks at 452 nm, 573 nm, and 656 nm under 368 nm excitation. These peaks correspond to the characteristic intra-4f electronic transitions of Dy3+ ions, specifically, 4I13/2 to 6H15/2, 4F9/2 to 6H13/2, and 4F9/2 to 6H11/2, representing blue, yellow, and red emissions, respectively. Photoluminescence decay studies showed multi-exponential behavior, with the average lifetime decreasing from 641 mu s in undoped BZO to 492 mu s in Dy3+- doped samples attributed to enhanced non-radiative recombination pathways. Among the codopants, Li+ demonstrated the most significant improvement in luminescence intensity and thermal stability by mitigating defects and optimizing charge compensation.
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    Thermoluminescence in GdAl3(BO3)4 phosphors: Unusual heating rate dependencies, dose responses and kinetic parameters
    (Pergamon-Elsevier Science Ltd, 2023) Alajlani, Y.; Sonsuz, M.; Barad, A.; Kaynar, Uemit H.; Ayvacikli, M.; Topaksu, M.; Can, N.
    The current study focuses on the production of GdAl3(BO3)4 (GAB) phosphors using gel combustion. X-ray diffraction (XRD) and thermoluminescent (TL) methods were used to investigate the structural and thermolu-minescence (TL) features of the samples. XRD results revealed that GAB phosphors were crystallized in a rhombohedral crystal system. TL experimental data exhibited an unusual heating rate behaviour, which was explained by the semi-localized transition model, and this provides valuable insight into the properties of the GAB sample. Beta-irradiated GAB hosts exhibit two primary peaks at 106 degrees C and 277 degrees C on their TL glow curves. We have employed a variety of heating rates (VHRs), TM-Tstop method, and computerized glow curve decon-volution (CGCD) techniques. By using a combination of these techniques, we can identify the kinetic parameters of the GAB samples more accurately, including peak numbers, activation energy, and frequency factors. Both Tm- Tstop and CGCD techniques produce similar results in terms of trap numbers and trap depths. In the trap centers, electrons were trapped at 1.05 eV, 0.84 eV, 1.12 eV, 1.20 eV, 1.42 eV, 1.63 eV and 1.42 eV. There was a linear behaviour of GAB samples over a dose range of 0.1 Gy-10 Gy. GAB phosphors did not show any significant changes in TL response with repeated irradiation cycles, suggesting that it is a reliable radiation dosimeter. GAB is therefore a potential candidate for radiotherapy dose measurement based on these findings.
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    Thermoluminescence study and evaluation of trapping parameters of samarium doped barium silicate phosphor
    (Taylor & Francis Ltd, 2021) Alajlani, Y.; Oğlakçı, M.; Kaynar, Ümit H.; Ayvacıklı, M.; Portakal-Uçar, Z. G.; Topaksu, M.; Can, N.
    We report the detailed analysis of thermoluminescence (TL) glow curves and the evaluation of kinetic parameters of Sm3+-incorporated BaSi(2)O(5.)The effect of various heating rates on TL kinetics and glow peak temperatures of Sm3+-doped BaSi2O5 phosphors exposed to beta particle irradiation at room temperature are investigated. The glow curve of the phosphor exposed to beta-irradiation consists of two main peaks with maxima at about 91 degrees C and 193 degrees C and exhibits good linearity between 1 and 10 Gy. The activation energies and frequency factors of trap centers involved in the TL emission were calculated from the TL glow curve of the sample by means of variable heating rate (VHR), repeated initial rise (RIR), and computerized glow-curve deconvolution (CGCD). Analysis of the main dosimetric peak techniques indicate that activation energies (E) and pre-exponential factor (s) vary between 0.93 and 1.72 eV, 10(10) and 10(13) s(-1). It is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases. The behavior of the TL intensities and glow peak temperatures as a function of the heating rate are discussed with regards to thermal quenching.