Yazar "Souadi, G." seçeneğine göre listele
Listeleniyor 1 - 11 / 11
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe 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.Öğe 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.Öğe High temperature photoluminescence dependence and energy migration of Tb3+-Incorporated K3Y(BO2)6 phosphors(Pergamon-Elsevier Science Ltd, 2024) Souadi, G.; Hakami, O.; Kaynar, U. H.; Coban, M. B.; Aydin, H.; Madkhali, O.; Zelai, T.This study investigates the structural and photoluminescence (PL) characteristics of Tb3+-incorporated K3Y(BO2)(6) (KYBO) phosphors synthesized via a microwave-assisted sol-gel technique. X-ray diffraction (XRD) and Rietveld refinement confirmed the formation of a pure hexagonal phase, with lattice expansion due to Tb3+ doping. PL studies revealed strong green emissions centered at 541 nm, attributed to the D-5(4) -> F-7(5) transitions of Tb3+ ions, with the highest intensity observed at 5 wt% Tb3+. A decrease in emission was observed at higher concentrations due to concentration quenching. Temperature-dependent PL measurements revealed reverse thermal quenching enhancing PL intensity. Chromaticity analysis based on CIE 1931 coordinates showed stable green emission across all concentrations, with a maximum color purity of 89.74% observed for the KYBO:3 wt% Tb3+ sample. The results, along with reverse thermal quenching behavior observed between 470K and 550K, suggest that these phosphors exhibit excellent potential for lighting and display technologies.Öğe 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.Öğe Photoluminescence properties and structural analysis of Tb3+-doped K3Gd (BO2)6: A first study on negative thermal quenching(Elsevier Science Sa, 2025) Souadi, G.; Madkhli, A. Y.; Kaynar, U. H.; Gok, C.; Aydin, H.; Coban, M. B.; Kaynar, S. CamIn this study, Tb3+-doped K3Gd(BO2)6 phosphors were synthesized using the microwave-assisted sol-gel method to explore their photoluminescence (PL) properties and thermal stability. XRD and Rietveld refinement confirmed the incorporation of Tb3+ions, without secondary phases. PL analysis revealed a strong green emission near 542 nm, attributed to the 5 D 4 -> 7 F 5 transition of Tb3+ions. An optimal Tb3+concentration of 3 wt% was identified, beyond which concentration quenching significantly reduced luminescence intensity. Radiative energy transfer, occurring via reabsorption, was observed at lower concentrations, facilitating efficient energy migration. Conversely, at higher concentrations, non-radiative processes such as cross-relaxation dominated. Remarkably, negative thermal quenching (NTQ) was observed up to 470 K, with an activation energy of 0.96 eV. Additionally, Na+ co- doping introduced lattice distortions that enhanced energy transfer between Tb3+ions and improved luminescence efficiency. The chromaticity diagram highlighted a shift towards the yellow-green region with increasing the Tb3+concentration, demonstrating tunable emission properties for solid-state lighting applications.Öğe 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. EkdalThis 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.Öğe Thermoluminescence behaviour and kinetic analysis of a novel Tb3+-Doped LaCa4O(BO3)3 phosphor: Impacts of heating rates and dose(Elsevier Sci Ltd, 2025) Madkhali, O.; Bulcar, K.; Barad, A.; Zelai, T.; Souadi, G.; Alathlawi, Hussain J.; Kaynar, U. H.This study employs kinetic analysis methods to comprehensively understand the thermoluminescence (TL) behaviour of Tb3+-doped LaCa4O(BO3)3 ( LACOB ), applying the Hoogenstraaten and Booth-Bohun-Parfianovitch methods, as well as the T m-T stop and Glow Curve Deconvolution (GCD) techniques. Optimal TL intensity was found at a Tb3+concentration of 2 wt%, beyond which concentration quenching occurred. The complete TL glow curve before preheating displays two peaks at approximately 70 degrees C and 286 degrees C. After preheating, only the 286 degrees C peak remains, due to its greater stability and intensity, making it the primary TL peak relevant for dosimetric applications. As the heating rate increased, the TL glow peaks shifted to higher temperatures and exhibited reduced intensity due to thermal quenching. The TL intensity exhibited superlinear behaviour at lower doses (0.5-20 Gy), followed by nearly linear behaviour at intermediate doses (30-100 Gy), and sublinear behaviour at higher doses. Anomalous fading of the TL signal was observed in LACOB:2 wt%Tb, suggesting competition with radiationless transitions. Activation energy values derived from Hoogenstraaten and Booth-Bohun-Parfianovitch methods showed close alignment, supporting the reliability of the kinetic analysis. The T m-T stop and GCD analyses with preheating identified four distinct TL glow peaks, with activation energies between 1.72 and 1.82 eV. Analysis whole glow curve revealed nine TL glow peaks overall, ranging from 1.08 to 1.82 eV, reflecting a complex trap structure with continuous energy distributions. The GCD method yielded a Figure of Merit (FOM) of 2.67 % with preheating and 2.84 without preheating, indicating a strong fit between experimental and theoretical data in both cases. The material demonstrated excellent stability and reusability, making it a strong candidate for dosimetric applications.Öğe 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.Öğe 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.Öğe Undoped and Eu doped LaCa₄O(BO₃)₃ phosphors: Thermoluminescence characteristics with a focus on kinetic parameters, anomalous heating rate, and dose response(Elsevier Ltd, 2025) Bulcar, K.; Portakal-Uçar, Z.G.; Zelai, T.; Souadi, G.; Hakami, O.; Kaynar, U.H.; Madkhali, O.The thermoluminescence (TL) properties of LaCa₄O(BO₃)₃ (LACOB) phosphors, both undoped and doped with 0.5 % Eu³⁺, were synthesized using a microwave-assisted sol-gel method and analysed under beta irradiation doses ranging from 0.1 Gy to 700 Gy. The TL glow curves revealed prominent peaks at 100 °C and 285 °C for the Eu-doped sample. Activation energy values were calculated using the Hoogenstraaten and Booth-Bohun-Parfianovitch methods, yielding 1.52 eV and 1.48 eV for the undoped sample, and 2.07 eV and 2.01 eV for the Eu-doped sample, respectively. Eu³⁺ ions introduced deeper traps and enhanced the thermal stability of the material. Anomalous increases in TL intensity with rising heating rates were observed, deviating from typical thermal quenching behaviour; this phenomenon was explained using a semi-localized transition (SLT) model. The TL reusability measurements demonstrated a standard deviation of less than 5 %, indicating consistent and reliable performance across multiple cycles. The TL glow curve deconvolution identified six distinct peaks in the undoped sample, while the Eu-doped sample showed a more complex trap structure with eight peaks, indicating the introduction of additional or modified trapping sites by Eu doping. The figure of merit (FOM) values obtained from the deconvolution analysis were all below 2.5 %, indicating a good fit between the observed and fitted TL signals. These findings suggest that Eu³⁺-doped LACOB is a robust material for radiation dosimetry, with its enhanced sensitivity, stability, and versatility across various dosimetric applications. © 2024 Elsevier Ltd and Techna Group S.r.l.Öğe 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.
