Browsing by Author "Kaynar Ü.H."
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Item Modeling of thorium (IV) ions adsorption onto a novel adsorbent material silicon dioxide nano-balls using response surface methodology(Elsevier Ltd, 2016) Kaynar Ü.H.; Şabikoğlu I.; Kaynar S.Ç.; Eral M.The silicon dioxide nano-balls (nano-SiO2) were prepared for the adsorption of thorium (IV) ions from aqueous solution. The synthesized silicon dioxide nano-balls were characterized by Scanning Electron Microscopy/Energy Dispersive X-ray, X-ray Diffraction, Fourier Transform Infrared and BET surface area measurement spectroscopy. The effects of pH, concentration, temperature and the solid–liquid ratio on the adsorption of thorium by nano-balls were optimized using central composite design of response surface methodology. The interaction between four variables was studied and modelled. Furthermore, the statistical analysis of the results was done. Analysis of variance revealed that all of the single effects found statistically significant on the sorption of Th(IV). Probability F-values (F=4.64–14) and correlation coefficients (R2=0.99 for Th(IV)) indicate that model fit the experimental data well. The ability of this material to remove Th(IV) from aqueous solution was characterized by Langmuir, Freunlinch and Temkin adsorption isotherms. The adsorption capacity of thorium (IV) achieved 188.2 mg g−1. Thermodynamic parameters were determined and discussed. The batch adsorption condition with respect to interfering ions was tested. The results indicated that silicon dioxide nano-balls were suitable as sorbent material for adsorption and recovery of Th(IV) ions from aqueous solutions. © 2016 Elsevier LtdItem An efficient removal of RB5 from aqueous solution by adsorption onto nano-ZnO/Chitosan composite beads(Elsevier B.V., 2017) Çınar S.; Kaynar Ü.H.; Aydemir T.; Çam Kaynar S.; Ayvacıklı M.In this study, the removal of Reactive Black 5 (RB-5) by nano-ZnO/Chitosan composite beads (nano-ZnO/CT-CB) from aqueous solution was investigated. ZnO nanoparticles were prepared by the via the microwave-assisted combustion technique. And then nano-ZnO/Chitosan composite beads were prepared by polymerization in the presence of nano-ZnO and chitosan. Characterization of composite beads were conducted using SEM, TEM, FTIR, TGA and XRD. Several important parameters influencing the removal of RB 5 such as contact time, pH and temperature were investigated systematically by batch experiments. At optimum conditions of pH 4 and adsorbent concentration of 0.2 g, dye removal efficiency was found 76%. Langmuir, Freundlich and Temkin adsorption models were used to describe adsorption isotherms and constants. The maximum adsorption capacity (qm) by Langmuir isotherm has been found to be 189.44 mg/g. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption. The positive value of the enthalpy change (32.7 kJ/mol) indicated that the adsorption is an endothermic process. The obtained results showed that the tested adsorbents are efficient and alternate low-cost adsorbent for removal of dyes from aqueous media. © 2016 Elsevier B.V.Item Modelling and Optimization of Uranium (VI) Ions Adsorption Onto Nano-ZnO/Chitosan Bio-composite Beads with Response Surface Methodology (RSM)(Springer New York LLC, 2018) Kaynar Ü.H.; Çınar S.; Çam Kaynar S.; Ayvacıklı M.; Aydemir T.Nano-ZnO-chitosan bio-composite beads were prepared for the sorption of UO22+ from aqueous media. The resulting nano-ZnO/CTS bio-composite beads were characterized by TEM, XRD etc. The sorption of UO22+ by bio-composite beads was optimized using RSM. The correlation between four variables was modelled and studied. According to RSM data, correlation coefficients (R2 = 0.99) and probability F-values (F = 2.24 × 10− 10) show that the model fits the experimental data well. Adsorption capacity for nano-ZnO/CTS bio-composite beads was obtained at 148.7 mg/g under optimum conditions. The results indicate that nano-ZnO/CTS bio-composite beads are appropriate for the adsorption of UO22+ ions from aqueous media. Also, the suitability of adsorption values to adsorption isotherms was researched and thermodynamic data were calculated. © 2017, Springer Science+Business Media, LLC.Item Preparation and cathodoluminescence characteristics of rare earth activated BaAl2O4 phosphors(Elsevier Ltd, 2018) Benourdja S.; Kaynar Ü.H.; Ayvacikli M.; Karabulut Y.; Guinea J.G.; Canimoglu A.; Chahed L.; Can N.Undoped and Pr, Sm and Tb activated BaAl2O4 phosphors have been synthesized by solid state reaction method and combustion method. The structure and morphological observation of the phosphor samples were monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF♯17–306). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). Undoped BaAl2O4 sample exhibits a broad defect emission from 300 to 500 nm from the aluminate defect centres. CL spectra recorded at room temperature display that the as-prepared BaAl2O4:Ln (Ln=Pr, Sm and Tb) phosphors exhibit different luminescence colors coming from different rare earth activator ions. The transition 4G5/2 → 6H7/2 located at 606 and 610 nm for Sm3+ can occur as hypersensitive transition having the selection rule ΔJ = ± 1. For the Tb3+ doped samples, they exhibit D45 green line emissions. The proposed luminescent mechanisms of all doped rare earth ions are also discussed. © 2018 Elsevier LtdItem Anomalous heating rate response of beta irradiated Sm3+ and Tb3+ doped BaAl2O4 phosphors(Elsevier Ltd, 2018) Kaynar Ü.H.; Guvener E.; Ayvacikli M.; Dogan T.; Balci-Yegen S.; Oglakci M.; Topaksu M.; Karabulut Y.; Canimoglu A.; Benourdja S.; Can N.The stuffed derivative of the tridymite structure, the oxide BaAl2O4 has been regarded as a long persistent phosphor. Thermoluminescence (TL) glow curve peaks of thin pellet samples of undoped and, Sm3+ and Tb3+ doped BaAl2O4 prepared by combustion method was reported. The structure of the compounds was monitored by X-ray diffraction and found a single-phase compound with a hexagonal structure. Performing a series of TL measurements for the temperature range from room temperature to 400 °C, the effect of beta radiation dose on TL response, various TL heating rate (HR) properties of undoped and Sm3+ and Tb3+ doped BaAl2O4 phosphors were investigated. Peak shape method was also utilized to assess the trap parameters. The activation energy of the main peak at 128 °C was found to be 0.97 eV. TL glow curves obtained from undoped and Tb3+ doped BaAl2O4 decrease with increasing HR value (varying from 0.5 to 15 °C s−1) in a way matching with thermal quenching effect. Contrary to expectations, anomalous HR dependence was observed on Sm3+ doped BaAl2O4 sample and a semi-localized transition model has been used in order to explain such behaviour. © 2018 Elsevier B.V.Item Sorption of uranium(VI) from aqueous solutions by DEEA organo-volcanic: isotherms, kinetic and thermodynamic studies(Springer Singapore, 2018) Kaynar Ü.H.; Hiçsönmez Ü.; Çam Kaynar S.; Koçak S.The sorption of the uranium(VI) ions from aqueous solutions by diethylethanolammonium organo-volcanics (Kula-TURKEY) was investigated under different experimental conditions. DEEA was used to modify the surface of basaltic volcanics. The characteristic of basaltic volcanic was analyzed by XRF, SEM–EDS, FTIR, and XRD. The BET surface areas of unmodified volcanics and DEEA-modified volcanics were found as 2.265 and 3.689 m2/g, respectively. The volcanic samples were treated by using different concentrations of DEEA. The adsorption of U(VI) on natural and modified volcanics was examined as a function of the contact time, initial pH of the solution, initial U(VI) concentration, and temperature. Langmuir, Freundlich, and D–R adsorption isotherms were used to describe the adsorption. While examining the adsorption percentage and distribution coefficient, these values for unmodified volcanics were found to be 25% ± 0.76 and 10.08 mL/g, while the values for the DEEA-modified volcanics were 88% ± 1.04 and 220 mL/g, respectively. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. In this study, it can be seen that the adsorption process is suitable for the pseudo-second-order kinetic model. Various thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were calculated with the thermodynamic distribution coefficients obtained at different temperatures. The sorption process was a chemical adsorption process. The results indicated that the processes are spontaneous and endothermic. © 2018, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Chinese Nuclear Society, Science Press China and Springer Nature Singapore Pte Ltd.Item A modeling and optimization study by response surface methodology (RSM) on UO2 2+ ions adsorption using nano-MgO particles prepared with combustion synthesis(Taylor and Francis Inc., 2018) Kaynar Ü.H.Nano-MgO particles were made for the adsorption of UO2 2+ from aqueous solutions. The obtained MgO nanoparticles were characterized by FTIR, XRD and SEM. The adsorption of UO2 2+ by particle was optimized with RSM. Coefficients of correlation (R2 = 0.99) and probability F-values (F = 3.1 10−10) reveal that the model is very good for the experimental data. Under optimum conditions, the adsorption capacity of nano-MgO particles was found to be 128.4 mg g−1. The results showed that nano-MgO particles were suitable for the sorption of UO2 2+ ions from aqueous solutions. In addition, the adsorption isotherms and the thermodynamic parameters were examined. © 2018, © 2018 Taylor & Francis Group, LLC.Item Method for the determination of polonium-210 in tea samples using response surface methodology (RSM)(Springer, 2019) Çam Kaynar S.; Kaynar Ü.H.The method based on solvent parameters (mass, cycle of acidification, and autodeposition time), combined with response surface methodology (RSM) modeling and optimization, has been developed for maximizing 210 Po activity in tea samples, as observed by an alpha spectrometer. RSM based on 3-factor and 5-level composite center design was used to obtain the optimal combination of solvent conditions. As solvent parameters for 210 Po activity, different masses (0.5, 0.75, 1, 1.5, and 2 g), different cycles of acidification (2, 3, 4, 5, and 6 times), and different autodeposition times (2, 3, 4, 5, and 6 h) were studied. The 3D response surface plot and the contour plot derived from the mathematical models were used to determine the optimal conditions. According to the obtained results, the experimental value of 210 Po activity was in good agreement (R 2 = 0.96) with the value predicted by the model. We found a favorable effect of mass on the 210 Po activity (p < 0.05). © 2019, China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd.Item Cathodoluminescence properties of La2MoO6:Ln3+ (Ln: Eu, Dy, and Sm) phosphors(Elsevier Ltd, 2020) Ayvacikli M.; Kaynar Ü.H.; Karabulut Y.; Guinea J.G.; Bulcar K.; Can N.La2MoO6 orange-red phosphors with high efficiency incorporated with Eu, Dy and Sm have been synthesized through a gel combustion method. The influences of rare earth doping in synthesized samples were analysed by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and cathodoluminescence. Rare earth doped La2MoO6 samples show strong emission bands in the range of 400–750 nm and optimal doping concentration for all samples was 2 mol%. La2MoO6 host doped Eu ion showed intense and predominant emission peaks in 450–750 nm range. The electrical multipolar interaction contributed to the non-radiative energy transfer between Eu3+ ions in La2MoO6 host matrix. Sm doped La2MoO6 host exhibited orange-red CL emission peaks at 564, 608, 652 and 708 nm La2MoO6:Dy3+ phosphor displayed emissions at 484, 574 and 670 nm, respectively. The observed intense and sharp emission peaks indicate that La2MoO6 is promising host for lanthanides doped phosphor materials in the applications of optoelectronic. © 2020 Elsevier LtdItem Synthesis and competitive luminescence quenching mechanism of Ca3Al2O6:Ln3+ (Ln: Dy and Sm) phosphors(Elsevier Ltd, 2020) Bakr M.; Kaynar Ü.H.; Ayvacikli M.; Benourdja S.; Karabulut Y.; Hammoudeh A.; Can N.Sm3+ and Dy3+ activated Ca3Al2O6 phosphors were produced through a gel combustion method using Urea + β-Alanine, Urea, and Urea + Glycine as fuels. The crystal structure and the phase purity of the obtained materials were characterized by X-ray powder diffraction (XRD). Ca3Al2O6:Sm3+ phosphor shows characteristic emission lines (565 nm, 602 nm, 649 nm, and 714 nm) in the orange red region assigned to 4G5/2→6HJ (J = 5/2, 7/2, 9/2, 11/2) transitions of Sm3+. The strongest peak is located at 602 nm. Emission spectra of Ca3Al2O6:Dy3+ show that there are two dominant peaks centered at 480 nm and 573 nm emitting blue and yellow light. Optimum doping concentrations of Sm(NO3)3 and Dy(NO3)3 are 0.01 % and 0.03 %, respectively. The concentration quenching mechanism is verified to be a dipole-dipole interaction as the type of energy transfer among Sm3+-Sm3+ and Dy3+-Dy3+ ions. The critical distance is also calculated to be 24.19 Å and 16.77 Å, respectively. © 2020 Elsevier LtdItem Thermoluminescence properties of beta particle irradiated Ca3Al2O6 phosphor relative to environmental dosimetry(Elsevier B.V., 2020) Bakr M.; Portakal-Uçar Z.G.; Yüksel M.; Kaynar Ü.H.; Ayvacikli M.; Benourdja S.; Canimoglu A.; Topaksu M.; Hammoudeh A.; Can N.Undoped Ca3Al2O6 phosphor was successfully synthesized through a gel-combustion method using different fuels. It was characterized by X-ray diffraction (XRD) technique and its cubic phase structure was confirmed from XRD pattern. TL data were recorded from room temperature (RT) to 500 °C in the heating rate of 2 °C/s. The glow curves of Ca3Al2O6 sample exposed to different beta doses (0–200 Gy) exhibited a significant glow peak at about 184 °C. The TL intensity of the glow peak exhibited very good linearity between 0.1 and 10 Gy. Following this, it was decreased at higher doses which was referred to this effect as monotonic dose dependence. Initial rise (IR), peak shape (PS), and variable heating rate (VHR) methods were used to estimate trapping parameters. Computerized glow curve deconvolution (CGCD) method via TLAnal software was also applied to estimate the number of peaks and kinetic parameters corresponding to the main glow curve in Ca3Al2O6 sample. The trapping activation energy of the main dosimetric peak was calculated to be around 1.30 eV for all methods. Present findings confirm that Ca3Al2O6 host is a promising candidate for applications in environmental dosimetry as one depicts good TL dose response with adequate sensitivity and linearity. © 2020 Elsevier B.V.Item Cathodoluminescence and photoluminescence properties of Dy doped La2CaB10O19 phosphor(Elsevier B.V., 2020) Ayvacikli M.; Kaynar Ü.H.; Karabulut Y.; Guinea J.G.; Dogan T.; Can N.In this study, we report a detailed analysis of the photoluminescence (PL) and cathodoluminescence (CL) properties of La2CaB10O19 (LCB) doped with Dy ion. Dy doped LCB materials were successfully synthesized using a sol-gel combustion method. Dy doped LCB has the monoclinic structure with lattice parameters a = 11.02067 Å, b = 6.55755 Å, c = 9.10541 Å and α = γ = 90.00, and β = 91.49°. Under the excitation by a low voltage electron beam and pulse laser at 349 nm, the LCB:Dy3+ phosphor produces the characteristic emission bands of Dy3+ due to intra-configuration transitions of 4F9/2 → 6H15/2 (480 nm, blue), 4F9/2 → 6H13/2 (574 nm, yellow), 4F9/2 → 6H11/2 (662 nm, red) and 4F9/2 → 6H9/2 (752 nm, red). The concentration quenching phenomenon was observed in both CL and PL measurements and optimum doping concentration was estimated to be 2%. We suggest that the concentration quenching mechanism of intense yellow emission at 574 nm was attributed to dipole-dipole interaction for both CL and PL. © 2020 Elsevier B.V.Item Enhancing the blue luminescence behaviour of the Li co-doped novel phosphor ZnB2O4: Tm3+(Elsevier Ltd, 2020) Kucuk N.; Kaynar Ü.H.; Akca S.; Alajlani Y.; Yin L.; Wang Y.; Garcia Guinea J.; Bulcar K.; Dogan T.; Karabulut Y.; Ayvacikli M.; Canimoglu A.; Topaksu M.; Can N.Here we report a detailed structural analysis, and properties of the cathodoluminescence (CL), photoluminescence (PL) and 3D thermoluminescence spectra of the Tm3+ incorporated ZnB2O4 phosphor successfully synthesized through wet-chemical synthesis. The formation of a single-phase compound is verified through X-ray diffraction (XRD) studies. The phosphor shows an efficient blue emission located at 458 nm corresponding to 1D2→3F4 under both a low voltage electron beam and UV excitation. The optimal concentration of the doped Tm3+ is 0.5 mol% in CL and PL measurements. The corresponding concentration quenching mechanism is confirmed to be a multipole-multipole interaction, and the critical distance between Tm3+ ions is estimated to be 34 Å. Incorporating Li+ remarkably enhances the luminescence intensity probably because of the charge compensation effect. Li ions are speculated to fill the defects in the ZnB2O4 host and then the excitation energy transfers from the host to Tm3+. Surprisingly, the thermoluminescence spectra of ZnB2O4:Tm3+ and Li+ co-doped ZnB2O4:Tm3+ recorded in the temperature range 30–400 °C follow a different pattern compared with PL and CL data. The dominant signals come from Tm3+ sites. Above room temperature, the Tm3+ ions do not show the peak temperature movement, but do exhibit a different pattern with the addition of co-doped Li+ ions. These results indicate that these phosphors are promising candidates for luminescence-based optoelectronic devices. © 2020 Elsevier B.V.Item Thermoluminescence behaviour of europium doped magnesium silicate after beta exposure(Elsevier B.V., 2020) Uçar Z.G.P.; Kaynar Ü.H.; Dogan T.; Souadi G.O.; Ayvacikli M.; Canimoglu A.; Topaksu M.; Can N.This article presents a detailed analysis of beta ray exposed thermoluminescence response of a series of Eu3+ doped (0.5–10 mol%) Mg2SiO4 nanocrystalline samples successfully synthesized through solid state reaction method. Optimizing the doping concentration of Eu3+ ion in Mg2SiO4 phosphor was found as 3 mol%. Two main peaks were seen at 246 °C and 374 °C and also low temperature peak at 78 °C. The intensities of these peaks were increased linearly with increasing beta absorbed dose. Tm−Tstop method was used to reveal trap levels. Variable heating rate and computerized glow curve deconvolution methods were also used to evaluate the number of peaks and kinetic parameters, namely activation energy and frequency factor. The results of a series of experiments carried out to investigate some fading characteristics of Mg2SiO4:Eu3+ were also presented. The findings suggest that thermoluminescence properties of Mg2SiO4:Eu3+ makes this material suitable and promising dosimetric phosphor material for medical applications. © 2020 Elsevier B.V.Item Synthesis and photoluminescence characteristics of Dy incorporated MoO3 phosphor: Suppression concentration quenching(Elsevier Ltd, 2020) Ayvacikli M.; Kaynar Ü.H.; Karabulut Y.; Canimoglu A.; Bakr M.; Akca S.; Can N.A series of MoO3:Dy3+ phosphors have been synthesized via the gel-combustion method. The X-ray and photoluminescence (PL) emission spectra were employed to characterize the obtained phosphors. The prepared samples were characterized through XRD measurements and exhibited that Dy3+ ions can be successfully incorporated into the host material. The PL emission bands of Dy3+ doped MoO3 were observed at 486 nm, 574 nm and 666 nm which are assigned to the transitions of 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2, respectively. Concentration quenching were largely taken into consideration as one of the crucial aspects limiting the application range of phosphors in today's modern world. An abnormal thermal quenching dependence was reported when Dy3+ ions were incorporated into MoO3 host matrix. In order to understand the origin of this beneficial behaviour, energy transfer processes occurring via radiative and nonradiative mechanisms were investigated to elucidate this suppression of the concentration quenching. © 2020 Elsevier LtdItem Eu3+ and Dy3+ doped La2MoO6 and La2Mo2O9 phosphors: Synthesis and luminescence properties(Elsevier Ltd, 2020) Kaynar Ü.H.; Cam Kaynar S.; Alajlani Y.; Ayvacikli M.; Karali E.; Karabulut Y.; Akca S.; Karali T.; Can N.We report a detailed structural analysis and properties of the photoluminescence (PL) and thermoluminescence (TL) spectra of Eu3+ and Dy3+ incorporated into novel La2MoO6 and La2Mo2O9 phosphors synthesized successfully through gel combustion synthesis. The formation of a tetragonal phase and a cubic structure were verified for La2MoO6 and La2Mo2O9 phosphors via X-ray diffraction (XRD) studies. Dy doped samples exhibited blue and green emissions at 480 nm (4F9/2 →6H15/2) and 572 nm (4F9/2 → 6H13/2), and also Eu doped samples showed a sharp emission peaks at 612 and 619 nm (5D0 →7F2) upon 349 nm pulse laser excitation. Peak shape (PS) technique was utilised to determine activation energy, frequency factor and order of kinetics associated with the main glow curves in undoped and Eu and Dy doped samples after X-ray irradiation. The present findings suggest that Eu and Dy incorporated La2MoO6 and La2Mo2O9 phosphors are highly auspicious candidates for applications in solid-state lighting. © 2019 Elsevier LtdItem Influence of laser excitation power on temperature-dependent luminescence behaviour of Ce- and Tb-incorporated BaMgAl10O17 phosphors(Elsevier Ltd, 2020) Kaynar Ü.H.; Kaynar S.C.; Ayvacikli M.; Karabulut Y.; Souadi G.O.; Can N.BaMgAl10O17 (BAM) is a highly suitable host lattice for various rare earth ions with excellent luminescence properties in different spectral regions, including a strong photoluminescence (PL) emission from the visible spectral region. A new Ce- and Tb-incorporated BaMgAl10O17 phase was synthesized successfully using a wet combustion method and it was studied as a function of the temperature and laser excitation power. We further characterize the obtained phosphors with X-ray diffraction at room temperature. Different fuel/oxidant (f/o) ratios were introduced to investigate the optimum synthesis conditions for the BAM phosphors and optimum ratio was found out to be 8. The photoluminescence (PL) spectra were collected under the excitation light generated by a Nd:YLF pulse laser at 349 nm as the temperature was increased from 10 K to 300 K. A strong green emission of Tb3+ was observed in the green region of the spectrum due to the 5D4→7FJ transition. We also observed a wide emission band from the Ce3+ ion in the wavelength range of 350–650 nm. The luminescence intensities of all phosphors exhibited different patterns with an increase in the temperature. We also evaluated how the PL spectrum of the rare earth-activated BAM host matrix shifts under various laser excitation powers. The PL intensity of Ce-activated BAM significantly shifted (~30 A) to the blue region of the spectrum with an increase in the laser excitation power, however we did observed no shift forTb3+ activated BAM. The present findings suggest that Tb-incorporated BaMgAl10O17 can be effective as a green phosphor candidate material with a wide range of applications. © 2019 Elsevier LtdItem Structural and temperature-dependent luminescence of Terbium doped YAl3(BO3)4 phosphor synthesized by the combustion method(Elsevier Ltd, 2022) Hakami J.; Kaynar Ü.H.; Ayvacikli M.; Coban M.B.; Garcia-Guinea J.; Townsend P.D.; Oglakci M.; Can N.A 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 activation 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. © 2022 Elsevier Ltd and Techna Group S.r.l.Item Dy3+ and Eu3+ co-activated gadolinium aluminate borate phosphor: Synthesis, enhanced luminescence, energy transfer and tunable color(Elsevier Ltd, 2023) Madkhali O.; Kaynar Ü.H.; Cam Kaynar S.; Ayvacikli M.; Can N.The synthesis of GdAl3(BO3)4 phosphors incorporated with activators of Dy3+ and Dy3+/ Eu3+was successful and achieved through the gel combustion method. Powder X-ray diffraction (XRD) was employed to identify phase purity and the effects of dopant concentration on the crystallographic structure. The results of Photoluminescence (PL) measurements revealed that the intensity and lifetime of luminescence properties varied depending on the concentrations of Dy3+ and Eu3+ ions. The dependence of luminescence intensity on doping concentration is investigated with respect to the energy transfer process between Eu3+ and Dy3+ ions. A decrease in luminescence lifetime occurs with increasing concentrations of Eu3+ co-doping. The energy transfer was also investigated using decay curve analysis. The co-doping of Eu3+ significantly boosts the energy transfer efficiency from 26% to 84%. These findings make GdAl3(BO3)4: Dy3+, Eu3+ phosphors an ideal choice for LED applications in solid state lighting and displays. © 2023 Elsevier LtdItem Thermoluminescence in GdAl3(BO3)4 phosphors: Unusual heating rate dependencies, dose responses and kinetic parameters(Elsevier Ltd, 2023) Alajlani Y.; Sonsuz M.; Barad A.; Kaynar Ü.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 thermoluminescence (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 °C and 277 °C on their TL glow curves. We have employed a variety of heating rates (VHRs), TM-Tstop method, and computerized glow curve deconvolution (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. © 2023 Elsevier Ltd