Browsing by Author "Coban, MB"
Now showing 1 - 20 of 20
Results Per Page
Sort Options
Item Phase transition and luminescence characteristics of dysprosium doped strontium stannate phosphor synthesized using hydrothermal methodKaynar, H; Coban, MB; Madkhli, AY; Ayvacikli, M; Can, NA series of strontium stannate (SrSnO3) doped with Dy3+ ions at various wt % concentrations (1, 2, 3 and 5) were synthesized via hydrothermal reaction and analysed using X-ray diffraction (XRD), energy dispersive spectros-copy (EDS), environmental electron scanning microscope (ESEM), photoluminescence (PL) and, cath-odoluminescence (CL). The XRD results confirmed that all samples were assigned to cubic perovskite-type SrSnO3 structured with the Pm3m space group. The PL emission spectrum of Dy3+ activated samples consisted of some characteristic peaks located at 481 nm, 572 nm, 660 nm and 753 nm, corresponding to (4F9/2 -> 6H15/2, blue), (4F9/2 -> 6H13/2, yellow), 660 nm (4F9/2 -> 6H11/2, red) and 753 nm (4F9/2 -> 6H9/2, red) transitions. The PL emission line intensity is gradually enhanced with an increase in doping concentration up to 3 wt %, followed by concentration quenching. The confinement effects of localized resonant energy transfer might cause higher concentration quenching. PL emission spectra were affected by the temperature range from 10 K to 300 K. PL emission anomalies at 270 K in SrSnO3:Dy3+ have been reported to be consistent with a structural phase tran-sition at this temperature. This work confirms Singh et al.'s observation, revealing that SrSnO3 has a phase transition at 270 K.Item Novel Sm3+doped YCa4O(BO3)3 phosphors: Structural and, low and room temperature luminescent insightsSouadi, G; Amri, N; Kaynar, ÜH; Coban, MB; Madkhali, O; Ayvacikli, M; Can, NInorganic phosphors, known for their ability to capture energy from various sources and emit visible light, have become essential in the development of advanced lighting and display technologies. This study explores YCa4O (BO3)3 (YCOB) as a potential host material for phosphors, focusing on the luminescent properties of YCOB phosphors doped with Sm3+ ions. The successful integration of Sm3+ ions into the YCOB host lattice is confirmed through structural characterization using X-ray diffraction (XRD), Fourier -Transform Infrared Spectroscopy (FTIR), and Energy -Dispersive X-ray Spectroscopy (EDS). Photoluminescence (PL) studies reveal distinct emission spectra with Stark energy level splitting, indicating a cooperative effect between Y3+ and Sm3+ ions. Concentration quenching, mainly attributed to dipole -dipole (d -q) interactions, is observed at higher Sm3+ concentrations. Temperature -dependent PL measurements demonstrate thermal quenching at lower temperatures and increased emission intensity with higher laser power. Thermal quenching is explained by reduced lattice vibrations and electron -phonon interactions, leading to decreased radiative recombination of charge carriers. The CIE chromaticity data position the samples in the orange -red region, emitting vibrant orange -red light. This comprehensive investigation provides insights into the synthesis and luminescent properties of YCOB:Sm3+ phosphors, highlighting their potential applications in luminescent devices.Item Synthesis and photoluminescence characteristics of a novel Eu and Tb doped Li2MoO4 phosphorSouadi, G; Kaynar, UH; Ayvacikli, M; Coban, MB; Oglakci, M; Canimoglu, A; Can, NLi2MoO4: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.Item Characterization, room and low temperature photoluminescence of yttrium aluminium borate activated with Sm3+ionsMadkhli, AY; Kaynar, UH; Coban, MB; Ayvacikli, M; Canimoglu, A; Can, NIn this study, the combustion method assisted by urea that is ideally suited to economic and time saving was used for the synthesizing of reddish orange emitting YAl3(BO3)4 phosphor samples doped with various Sm3+ ions (from 0.01 wt% to 7wt%). A detailed study of the structural and luminescence properties at room/low tem-perature of the synthesized samples was performed. XRD analysis revealed a rhombohedral structure with an R32 space group (155). The particle size was determined by the Scherrer's method to be 48 nm. The visible PL emission spectra upon excitation at 359 nm are recorded and four emission peaks around 564, 599, 646, and 707 nm with transitions 4G5/2 -> 6H5/2, 4G5/2 -> 6H7/2, 4G5/2 -> 6H9/2 and 4G5/2 -> 6H11/2 are observed. Concentration quenching was mainly caused by dipole-dipole interactions between neighbouring trivalent Sm3+ ions. Through the CIE chroma coordinates (0.606, 0.382), the optimized sample (x = 0.03) demonstrates admirable luminous performance. YAl3(BO3)4:Sm3+ can be a good candidate for use as a red component for lighting applications.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 Structural and thermal insights into the luminescent behavior of Dy3+-Doped BaZrO3 with alkali metal codopants under UV radiationArslanlar, YT; Alajlani, Y; Coban, MB; Kaynar, UH; Aydin, H; Örücü, H; Guinea, JG; Can, NThis 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.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 Synthesis, characterization and enhanced photoluminescence and temperature dependence of ZrO2:Dy3+phosphors upon incorporation of K plus ionsCan, N; Coban, MB; Souadi, G; Kaynar, ÜH; Ayvacikli, M; Guinea, JG; Karali, EEThis 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.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.Item Photoluminescence properties and structural analysis of Tb3+-doped K3Gd (BO2)6: A first study on negative thermal quenchingSouadi, G; Madkhli, AY; Kaynar, UH; Gok, C; Aydin, H; Coban, MB; Kaynar, SC; Ayvacikli, M; Can, NIn 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.Item High temperature photoluminescence dependence and energy migration of Tb3+-Incorporated K3Y(BO2)6 phosphorsSouadi, G; Hakami, O; Kaynar, UH; Coban, MB; Aydin, H; Madkhali, O; Zelai, T; Ayvacikli, M; Can, NThis 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.Item Structural and temperature-dependent luminescence of Terbium doped YAl3(BO3)4 phosphor synthesized by the combustion methodHakami, J; Kaynar, UH; Ayvacikli, M; Coban, MB; Garcia-Guinea, J; Townsend, PD; Oglakci, M; Can, NA series of Y1-xAl3(BO3)4:x Tb3+ (x = 0.5 to 7 wt%) phosphors synthesized by a gel combustion method have been systemically investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive spectroscopy (EDS), and photoluminescence (PL) as a function of temperature from 300 K to 10 K and 300 K-550 K. An XRD analysis confirms that the phosphors crystallized, and its crystal structure was analysed. The synthesized phosphor matches the XRD pattern provided in the ICSD File No 96-152-6006. The FTIR analysis indicates that nitrates and organic matter have been completely removed and the BO3 groups are present. The broad PL band peaked at 420 nm with a shoulder circa 460 nm of YAl3(BO3)4 is associated with hydrous components which attached to the sample in environmental conditions after synthesis. The PL spectra of YAl3(BO3):Tb3+ phosphors exhibit a bright and narrow green main emission peak at 543 nm corresponding to the 5D4 -> 7F5 transition under 359 nm excitation. The PL intensity increases with increasing Tb3+ ion concentration up to 5 wt %, followed by evidence for concentration quenching. There is a possibility that higher concentration quenching could be from confinement effects of localised resonant energy transfer. PL data revealed that acti-vation energies for thermal quenching at 485 nm and 543 nm were found to be 0.659 and 0.092 eV, and 0.585 and 0.087 eV, respectively.Item Structural and temperature dependence luminescence characteristics of RE (RE=Eu3+, Dy3+, Sm3+and Tb3+) in the new gadolinium aluminate borate phosphorMadkhali, O; Kaynar, H; Alajlani, Y; Coban, MB; Guinea, JG; Ayvacikli, M; Pierson, JF; Can, NGdAl3(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.Item Temperature-responsive insights: Investigating Eu3+and Dy3+activated yttrium calcium oxyborate phosphors for structure and luminescenceJabali, DA; Madkhli, AY; Souadi, G; Kaynar, UH; Coban, MB; Madkhali, O; Ayvacikli, M; Amri, N; Can, NAn investigation into the luminescent behavior of YCOB (Yttrium Calcium Oxyborate) doped with Eu3+ and Dy3+ ions, synthesized via the combustion method, is presented. The study, employing X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Energy-Dispersive X-ray Spectroscopy (EDS) analyses, confirms the structural integrity and purity of the synthesized nanophosphors. An XRD pattern exhibiting distinct crystalline peaks indicates that the dopant ions were successfully integrated into the YCOB lattice. The photoluminescence (PL) response of YCOB with Eu3+ and Dy3+ ions is thoroughly examined, uncovering distinct excitation and emission spectra. In the case of Eu3+ doping, excitation spectra reveal a significant charge transfer (CT) band at 254 nm, indicative of electron transfer between oxygen and europium ions. This CT transition enhances our understanding of the excitation behavior, with the dominant and Laporte-forbidden 5D0 -> 7F2 transition. Characteristic peaks at 345 nm in the excitation spectra efficiently stimulate YCOB:Dy3+ when Dy3+ is used as a dopant. The primary emission peak at 585 nm corresponds to the hypersensitive electric dipole transition 4F9/2-6H13/2. Concentration quenching phenomena are observed, with a maximum Eu3+ concentration of 7 wt % attributed to the dipole-quadrupole interaction. Dy3+ doping, with a maximum concentration of 2 wt % primarily shows multipolar interactions, especially dipole-dipole interactions. The study extends to CIE chromaticity analysis, emphasizing Eu3+ doping's suitability for white light-emitting diode (WLED) applications and ensuring color stability. Conversely, varying Dy3+ concentrations do not yield consistent chromaticity coordinates. These findings have significant implications for the development of advanced phosphor materials across diverse applications, offering a roadmap for optimizing their optical performance.