Yazar "Jabali, D. A." seçeneğine göre listele

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  • Küçük Resim
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    Beta irradiation-induced thermoluminescence: Glow curve analysis and kinetic parameters in combustion-synthesized undoped Ca4YO(BO3)3
    (Pergamon-Elsevier Science Ltd, 2024) Madkhli, A. Y.; Jabali, D. A.; Souadi, G.; Sonsuz, M.; Kaynar, U. H.; Akca-Ozalp, S.; Ayvacikli, M.
    This study examines the thermoluminescent (TL) properties of undoped Ca4YO(BO3)3 phosphor, focusing on how it behaves under a variety of experimental conditions. The IRSL-TL 565 nm was chosen as the appropriate detection filter among various optical detection filter combinations. During the preheating trials conducted at a rate of 2 degrees C/s, the TL peak exhibited increased intensity, particularly around 200 degrees C. The experimental outcomes demonstrated a reliable linear relationship (R2 = 0.996 and b = 1.015) in the dose response of undoped preheated Ca4YO(BO3)3 within the range of 1-200 Gy. The investigation encompasses a range of techniques, including the TM-Tstop method, computerized glow curve deconvolution (CGCD) analysis, and theoretical modelling. The application of the TM-Tstop method to samples irradiated with a 5 Gy dose revealed distinct zones on the TM versus Tstop diagram, signifying the presence of at least two discernible components within the TL glow curve, specifically, a single general order kinetics peak and a continuous distribution. The analysis of activation energy versus preheated temperature exhibited a stepwise curve, indicating five trap levels with depths ranging between 1.13 eV and 1.40 eV. The CGCD method also revealed the superposition of at least five distinct TL glow peaks. It was observed that their activation energies were consistent with the Tm-Tstop experiment. Furthermore, the low Figure of Merit (FOM) value of 1.18% indicates high reliability in the goodness-of-fit measure. These findings affirm the reliability and effectiveness of the employed methods in characterizing the TL properties of the Ca4YO(BO3)3 phosphor under investigation. Theoretical models, including the semi-localized transition model, were introduced to explain anomalous observations in TL glow peak intensities and heating rate patterns. While providing a conceptual framework, these models may require adjustments to accurately capture the specific characteristics uncovered through CGCD analysis. As a potential application, the study suggests that the characterized TL properties of Ca4YO(BO3)3 phosphor could be utilized in dosimetric applications, such as radiation dose measurements, owing to its reliable linear response within a broad dose range.
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    Optical performance and luminescence properties of Dy3+-doped LaMgB5O10 phosphors
    (Elsevier, 2025) Hakami, Jabir; Kaynar, U. H.; Coban, M. B.; Aydin, H.; Alamri, R.; Jabali, D. A.; Can, N.
    Despite significant advancements in borate-based phosphors, improving luminescent efficiency and thermal stability, particularly at high temperatures, remains a persistent challenge. In this study, Dy3+-doped LaMgB5O10 (LMBO) phosphors were synthesized and characterized for their photoluminescent properties to address these issues. Under 344 nm excitation, the Dy3+-activated LMBO phosphors exhibited strong luminescence with characteristic peaks at 482 nm (blue), 578 nm (yellow), and 663 nm (red), corresponding to specific Dy3+ transitions. Optimal luminescence was achieved at a doping level of 2 wt% Dy3+, beyond which quenching effects reduced emission intensity. The critical quenching distance (Rc) was estimated at 24.66 & Aring;, indicating predominant non-radiative energy transfer. Moreover, thermal quenching was reduced, with the activation energy for thermal quenching determined to be 0.1975 eV, demonstrating that the material can maintain reasonable luminescence efficiency at elevated temperatures. Time-resolved photoluminescence spectroscopy revealed multi-exponential decay behavior, indicating the presence of multiple decay processes. The average luminescence lifetimes were calculated as 632 mu s for the 2 wt% Dy3+ sample and 539 mu s for the 3 wt% Dy3+ sample, with a clear concentration quenching effect observed at higher dopant levels. Colorimetric analysis in the CIE 1931 color space revealed a shift toward yellow with increasing Dy3+ concentration, achieving a correlated color temperature (CCT) of 6595 K at 2 wt% Dy3+. This shift supports the material's potential for photonic and lighting applications. These findings highlight a significant advancement in addressing the thermal stability issue in phosphor materials, making Dy3+-doped LMBO phosphors promising candidates for advanced photonic technologies.