Browsing by Author "Altowyan, AS"
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Item Synthesis and thermoluminescence behavior of novel Sm3+ doped YCa4O(BO3)3 under beta irradiationAltowyan, AS; Sonsuz, M; Kaynar, UH; Hakami, J; Portakal-Uçar, ZG; Ayvacikli, M; Topaksu, M; Can, NThis study investigates the luminescent properties and dosimetric potential of YCa 4 O(BO 3 ) 3 :0.5%Sm 3+ phosphor synthesized via the combustion method. Dose -response investigations unveil a noteworthy linear increment in thermoluminescence (TL) intensity, emphasizing a remarkable linearity spanning a broad dose range from 0.1 to 300 Gy. Unusual heating rate effects are explored, revealing a shift in TL glow curve peak temperature (i.e 200 degrees C) towards higher temperatures with increasing heating rate. Speculative models, including Kinetic Trapping Effect, Thermal Quenching Compensation, and Defect Activation Energy Changes, are proposed. The study employs the T max - T stop method to identify characterize glow curve peaks, and the Initial Rise method for the lowtemperature segment analysis, revealing seven distinct trap levels at various depths within the bandgap. Glow curve deconvolution using the Complex Glow Curve Deconvolution (CGCD) method delineates a multi -peak structure, offering valuable insights into luminescent mechanisms. The model exhibits a Figure of Merit (FOM) of 1.71%, within an acceptable range, affirming its reliability. However, interpretation of the activation energy and frequency factor values suggests intricate site processes, necessitating a nuanced analysis to understand the material 's luminescent characteristics. The YCa 4 O(BO 3 ) 3 :0.5%Sm 3+ phosphor demonstrates promising characteristics for precise dosimetry, with linear dose response, absence of saturation effects, and intriguing heating rate behavior.Item Thermoluminescence kinetic parameters of beta irradiated the zinc gallate phosphor using different methodsAltowyan, AS; Sonsuz, M; Kaynar, H; Hakami, J; Ayvacikli, M; Topaksu, M; Can, NThe ZnGa2O4 phosphor material was synthesised through the gel combustion method, and its structural characteristics were studied via X-ray powder diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The XRD result indicates the generation of ZnGa2O4 in spinal cubic phase with a 25 nm crystalline size. The synthesized phosphor was irradiated using a90Sr/90Y source with a dose range of 0.1 Gy-100 Gy. For measuring thermoluminescence (TL), a linear heating rate of 2 degrees Cs 1 was applied to the sample in a temperature range of 25 degrees C-450 degrees C. The TL experiment revealed two peak maxima located at 180 degrees C and 304 degrees C and a shoulder around 70 degrees C. By preheating at 110 degrees C, the low temperature peak at 70 degrees C is removed. Both the depth and frequency factors of electron traps were determined using various heating rates (VHR), Tm-Tstop combined with initial rise (IR), and Computerised Glow Curve Deconvolution (CGCD). In both the Tm-Tstop and CGCD methods, six overlapping glow peaks were detected below the main glow peaks. The calculated activation energy values and peak maximum temperatures agree well with each other. The depths of electron traps calculated by different methods were found to be between 0.4 and 1.4 eV. We observed that both peak maximum temperatures and the area under glow peaks gradually decreased with an increase in the heating rate. Both Peak 1 and Peak 2 show sublinear relationship between 0.1-5Gy and 10-100 Gy. The findings of the present study show that the phosphors can serve as effective TLDs.Item Integrating K plus into Eu and Tb doped GdCa 4O(BO3)3: A dual study on photoluminescence and structureAltowyan, AS; Kaynar, UH; Hakami, J; Coban, MB; Ayvacikli, M; Aydin, H; Canimoglu, A; Can, NIn this study, we investigate the structural and photoluminescence (PL) properties of rare -earth -doped GdCa 4 O (BO 3 ) 3 (GdCOB) phosphors, specifically focusing on the spectral behaviour induced by doping with Eu 3 + and Tb 3 + ions. The powder X-ray diffraction (XRD) spectra confirm the formation of a monoclinic phase. The XRD data were also refined by a Rietveld refinement method. The existence of B, O, Ca, Gd, Tb, Eu and K elements was verified by EDS spectra. We introduce a detailed examination of the charge compensation process using Kro ger- Vink notation to clarify the mechanisms essential for tailoring the optical properties of the phosphors. The PL excitation spectrum of GdCOB:Eu 3 + , monitored at 611 nm, reveals sharp excitation peaks at 319, 361, 380, and 392 nm, corresponding to 7 F 0 -> 5 H 3 , 7 F 0 -> 5 D 4 , 7 F 0 -> 7 F 0 , and 7 F 0 -> 5 L 6 transitions, respectively. The PL spectrum under excitation of 392 nm exhibits that phosphors doped with Eu 3 + a significant red emission at 611 nm, which is attributed to the 5 D 0 -> 7 F 2 transition. This emission intensity is particularly enhanced at non-centrosymmetric sites of the Eu 3 + ions. Similarly, the PL excitation spectrum of GdCOB:Tb 3 + , monitored at 552 nm, displays distinct excitation peaks at 316, 341, 353, and 379 nm, which correspond to the transitions 7 F 6 -> 5 D 0, 7 F 6 -> 5 L 7, 7 F 6 -> 5 D 2, and 7 F 6 -> 5 D 3, respectively. Tb 3 +-doped phosphors display a bright green emission, with a dominant peak at 552 nm, resulting from the 5 D 4 -> 7 F 5 transition. Additionally, the introduction of K + ions as co-dopants results in modifications to the local environments of Eu 3 + and Tb 3 + ions. These changes allow for fine-tuning of the emission peaks, significantly enhancing the luminescent output of the phosphors. Optimal doping concentrations of 5 mol% for Eu 3 + and 1 mol% for Tb 3 + enhance luminescent intensity and prevent concentration quenching. This phenomenon, often resulting in reduced PL intensity at higher dopant levels, is primarily due to dipole -dipole interactions, consistent with Dexter's theory of energy transfer. Strategic modulation of doping concentrations, coupled with a deep understanding of energy transfer mechanisms are critical for the development of advanced luminescent materials Our analysis of the Commission de l ' Eclairage (CIE) chromaticity coordinates reveals enhanced energy transfer dynamics in rare -earth -doped borates, facilitating the tuning of luminescent properties. These results not only deepen our understanding of the fundamental physics governing such phosphors but also open pathways for the development of optoelectronic applications requiring consistent color output, such as LED technologies and solid-state lighting.Item Enhancement of luminescence and thermal stability in Eu3+-doped K3Y (BO2)6 with Li+ and Na+ co-dopingKaynar, UH; Aydin, H; Altowyan, AS; Hakami, J; Coban, MB; Ayvacikli, M; Karali, EE; Canimoglu, A; Can, NEu3+-doped and Li+/Na+ co-doped K3Y(BO2)6 (KYBO) phosphors were synthesized through a microwave- assisted sol-gel method, and their structural and photoluminescent (PL) characteristics were examined. X-ray diffraction (XRD) and Rietveld refinement confirm effective dopant incorporation and preservation of the crystalline structure. Fourier Transform Infrared (FTIR) spectroscopy indicates the maintenance of the borate structure, confirming the structural integrity of the phosphors upon doping. The addition of Li+ and Na+ co-dopants notably enhances luminescent efficiency and thermal stability, making these phosphors promising candidates for solid-state lighting (SSL) applications. PL analysis reveals strong red emission peaks at 612 nm, attributed to the 5 D o ? 7 F 2 transition of Eu3+ ions. The study indicates that electric dipole-quadrupole interactions are the primary mechanism for energy migration, with a critical distance of approximately 22.68 & Aring;. This mechanism contributes to concentration quenching at higher doping levels. High temperature PL measurements indicated an activation energy of 0.1389 eV for thermal quenching in the Li+ co-doped sample. Additionally, the Na+ co-doped sample exhibited an abnormal thermal stability behavior, with an even higher activation energy of 0.2536 eV. This suggests that Na+ co-doping significantly enhances the thermal resilience of the phosphor, making it more suitable for high-power light-emitting applications that operate under extreme conditions. CIE chromaticity diagrams highlight the potential for optimizing Eu3+ doping levels, combined with Li+ and Na+ co-doping, to improve luminescent performance and thermal stability for advanced SSL applications. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.Item Enhancement of luminescence and thermal stability in Eu3+-doped K3Y(BO2)6 with Li+ and Na+ co-doping (vol 35, 104695, 2024)Kaynar, UH; Aydin, H; Altowyan, AS; Hakami, J; Coban, MB; Ayvacikli, M; Karali, EE; Canimoglu, A; Can, NItem Novel Tb3+-Doped LaAl2 B4 O10 phosphors: Structural analysis, luminescent properties, and energy transfer mechanismKaynar, UH; Aydin, H; Hakami, J; Altowyan, AS; Coban, MB; Ayvacikli, M; Canimoglu, A; Can, NThis study explores the structural and luminescent properties of terbium (Tb3+)-doped lanthanum aluminium borate (LaAl2B4O,0, abbreviated as LAB) phosphors, a novel host lattice for Tb3+ doping. LAB:Tb3+ phosphors, with varying dopant concentrations, were synthesized using a microwave-assisted combustion synthesis approach and characterized using X-ray diffraction (XRD), Rietveld refinement, and photoluminescence spectroscopy at both room and low temperatures. The structural analysis confirmed the hexagonal crystal structure of LAB and revealed successful incorporation of Tb3+ ions without altering the fundamental lattice. Luminescence studies demonstrated that the LAB:Tb3+ phosphors show strong green emission primarily attributed to the 5D4 -> 7F5 transition of Tb3+. The optimal doping concentration was determined to be 5 wt% Tb3+, which provided maximum luminescence efficiency. This concentration also allowed for a critical study of energy transfer mechanisms within the phosphor, revealing dipole-dipole interactions with a critical distance of 9.80 & Aring; between Tb3+ ions. Additionally, the CIE chromaticity coordinates of LAB:0.05 Tb3+ were precisely determined to be (0.289, 0.4460), indicating the potential for high-quality green emission suitable for solid-state lighting and display technologies. This work not only demonstrates the potential of LAB:Tb3+ as a highly efficient green luminescent material, but also sheds light on the mechanisms responsible for energy transfer and concentration quenching.Item Structural and temperature-dependent photoluminescence properties of NaBaBO3:Ce3+,Tb3+phosphors synthesized using the combustionAltowyan, AS; Oglakci, M; Topaksu, M; Ozturk, E; Hakami, J; Coban, MB; Keskin, MO; Ayvacikli, M; Kaynar, UH; Canimoglu, A; Can, NThis 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.Item Structural and photoluminescent analysis of novel Eu3+ and Dy3+ Co-doped ZnO nanoparticles by incorporation of Li+ and K+ ionsAltowyan, AS; Coban, MB; Kaynar, UH; Çin, EA; Ayvacikli, M; Hakami, J; Can, NIn this study, we thoroughly investigate the structural and luminescent features of ZnO nanoparticles doped with Eu 3 + and co -doped with Dy 3 + , exploring the impact of Li + and K + incorporation during the precipitation process. The synthesized nanoparticles were comprehensively characterized using X-ray diffraction (XRD), Fourier transmission infrared (FTIR), Energy dispersive spectroscopy (EDS), and photoluminescence (PL) techniques. The XRD analysis conclusively verified the presence of the hexagonal wurtzite phase in the ZnO nanoparticles. PL assessment of undoped ZnO revealed a well-defined and narrow exciton band peaked at 390 nm, accompanied by a broad defect -related band spanning from 450 nm to 750 nm. For ZnO:Eu 3 + phosphors, distinct emission peaks emerged at 590 nm, 618 nm, and 696 nm when excited at 349 nm, corresponding to the 4 f electron transition inherent to Eu 3 + ions. The optimized doping level for the ZnO:xEu 3 + sample was determined to be 7 wt%. The mechanism of concentration quenching was identified as dipole -quadrupole interaction. Co -doping with Li + as a charge compensator resulted in a threefold enhancement in the luminescence intensity of the red -emitting ZnO: Eu 3 + , Li + . As the temperature decreases, the luminescence intensity of Eu 3 + transitions in ZnO:7 wt% Eu 3 + diminishes due to less efficient energy transfer among Eu 3 + ions, while the intrinsic broad band from ZnO fades away, emphasizing the temperature -sensitive nature of the material. The addition of Dy 3 + as a co-dopant to ZnO: Eu 3 + induces a counterintuitive effect, where an increase in Dy 3 + concentration unexpectedly results in a decrease in Eu 3 + emission peak intensity. This unconventional behavior highlights a complex interplay between Dy 3 + and Eu 3 + ions, suggesting the influence of spatial factors, competing processes, and potential dopant aggregation within the ZnO lattice. The CIE analysis conducted on ZnO:Eu 3 + , Dy 3 + , and Li + nanoparticles demonstrated precise control over the emitted light, enabling the fine-tuning of their optical properties for applications in displays.Item Lattice distortion effects induced by Li plus co-doping on ZnO:Tb3+phosphors: Photoluminescence and unusual hypersensitive 5D4 → 7F0 transitionAltowyan, AS; Coban, MB; Kaynar, UH; Hakami, J; Çin, EA; Kaynar, SC; Ayvacikli, M; Can, NA series of Tb3+, Li+ co-doped ZnO phosphors were prepared using a precipitation method. X-ray diffraction (XRD) analysis indicated the successful incorporation of Tb3+ into the ZnO lattice. The influence of Tb3+ doping content and Li+ charge compensator on the photoluminescence (PL) properties of ZnO:Tb3+ was investigated. Under UV excitation, emissions corresponding to electron transitions 5D4 -> 7FJ (J = 0,1,2,3,4,5,6) were observed from Tb3+ ions, including an unusual emission transition at 673 nm, which significantly enriches our understanding of Tb3+ luminescence. The critical concentration quenching of Tb3+ in ZnO:Tb3+ occurs at 7 mol%, as explained by the Van Uitert equation, which attributes this phenomenon to dipole-dipole interactions. Surprisingly, incorporating Li+ for charge balancing led to a reduction in the luminescence intensity of ZnO:7 mol% Tb3+, x%Li+ phosphors (x = 0.01 and 0.07) at 544 nm. This reduction highlights an increased degree of lattice distortion due to Li+ inclusion. Furthermore, CIE chromaticity analysis showed that the optimal doping concentration of 0.07 Tb3+ shifted the color coordinates towards vivid green, with a color temperature of approximately 6241 K, indicating of neutral white light.Item Temperature-dependent photoluminescence of novel Eu 3+ , Tb3+ , and Dy3+ doped LaCa4 O(BO3)3 : Insights at low and room temperaturesAltowyan, AS; Coban, MB; Kaynar, UH; Hakami, J; Ayvacikli, M; Hiziroglu, A; Can, NThis study explores the structural and optical qualities of LaCa4O(BO3)3 (LACOB) phosphors doped with Eu3+, Dy3+, and Tb3+ using a microwave-assisted sol-gel technique. It uncovers oxygen-related luminescence defects in LACOB, highlighting emission peaks at 489 and 585 nm for Dy3+, a distinct sharp peak at 611 nm for Eu3+ in the red spectrum, and a notable green emission for Tb3+ due to specific transitions. The photoluminescence (PL) analysis indicates that luminescence is optimized through precise doping, leveraging dipole interactions, and localized resonant energy transfer, which are influenced by dopant concentration and spatial configuration. Temperature studies show emission intensity variations, particularly noticeable below 100 K for Tb3+ doped samples, demonstrating the nuanced balance between thermal quenching and luminescence efficiency. This temperature dependency, alongside the identified optimal doping conditions, underscores the potential of these materials for advanced photonic applications, offering insights into their thermal behavior and emission mechanisms under different conditions.Item Enhanced luminescence of Eu3+ in LaAl2B4O10 via energy transfer from Dy3+ dopingKaynar, UH; Coban, MB; Hakami, J; Altowyan, AS; Aydin, H; Ayvacikli, M; Can, NIn this study, an investigation was conducted on the structural and photoluminescence (PL) characteristics of LaAl2B4O10 (LAB) phosphors initially incorporated with Dy3+ and Eu3+ ions. Subsequently, the impact of varying Eu3+ concentration while maintaining a constant Dy3+ concentration was examined. Structural characterization was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS). XRD analysis confirmed the effective embedding of both dopants into the hexagonal framework of the LAB. The PL emission spectra revealed characteristic emissions of Dy3+ (blue and yellow) and Eu3+ (red) ions. The optimized dopant concentrations of both Dy3+ and Eu3+ were observed to be 3 wt%. The dominant mechanism for concentration quenching in doped LAB phosphors was determined to be the electric dipole-dipole interaction. Co-doping with Eu3+ led to a substantial decrease in Dy3+ emission intensity (similar to 0.18-fold) while enhancing Eu3+ emission intensity (similar to 3.72-fold). The critical energy transfer distance (R-C = 11.64 & Aring;) and the analysis based on the Dexter theory confirmed that the energy transfer mechanism corresponds to dipole-dipole interaction. The color purities and correlated color temperatures (CCT) were estimated, suggesting the potential of these phosphors for warm white and red lighting applications, respectively. The observed energy transfer and luminescence properties, along with the structural and compositional characterization, highlight the promising potential of LAB:Dy3+/Eu3+ co-doped phosphors for advanced lighting and display technologies.