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Anomalous heating rate response of beta irradiated Sm3+ and Tb3+ doped BaAl2O4 phosphors
(Elsevier Science Sa, 2018) Kaynar, U. H.; Guvener, E.; Ayvacikli, M.; Dogan, T.; Balci-Yegen, S.; Oglakci, M.; Topaksu, M.
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 degrees 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 degrees 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 degrees 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. (C) 2018 Elsevier B.V. All rights reserved.
Cathodoluminescence and Raman characteristics of CaSO4:Tm3+, Cu phosphor
(ELSEVIER SCIENCE BV, 2015) Ekdal, E.; Garcia Guinea, J.; Kelemen, A.; Ayvacikli, M.; Canimoglu, A.; Jorge, A.; Can, N.
The physical characterization and phosphor emission spectra are presented for CaSO4 doped with Tm and Cu. All spectral wavelengths are related to electronic transitions of Tm3+ ions. The powder X-ray diffraction pattern showed that the compound exhibits orthorhombic structure and all reflections were indexed without any other secondary impurity phases. Chemical and structural properties of the samples have been characterized by means of Raman spectroscopy and environmental scanning electron microscope (ESEM) with an attached X-ray energy dispersive system (EDS). Group frequencies concept is essential point to the interpretation of the bands due to the main SO4 vibrational units and these displayed main characteristic intensive Raman bands including typical strong intensity at 1016 cm(-1) that corresponds to v(1)SO(4) vibrational mode. From the spatially-resolved cathodoluminescence (CL) spectrum, main emission bands of Tm3+ centered at 346, 362, and 452 nm, due to the respective transitions of P-3(0) -> H-3(4), D-1(2) -> H-3(6), D-1(2) -> F-3(4) were clearly identified. The study is novel as no such CL-ESEM data are available for this doped compound. (C) 2015 Elsevier B.V. All rights reserved.
Catholuminescence properties of rare earth doped CaSnO3 phosphor
(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Canimoglu, A.; Garcia-Guinea, J.; Karabulut, Y.; Ayvacikli, M.; Jorge, A.; Can, N.
The present study describes cathodoluminescence (CL) properties of CaSnO3 phosphors doped with Eu3+, Tb3+ and Dy3+ synthesized by a solid-state method. X-ray diffraction (XRD) patterns confirm that CaSnO3 sintered at 1200 degrees C exhibits orthorhombic structure. The evidence and rationale for two strong broad emission bands appeared at 360 and 780 nm for undoped CaSnO3 are presented. The CL measurements exhibit that the 4f-4f emissions from D-5(4) -> F-7(5) (490 nm), D-5(4) -> F-7(5) (544 nm), D-5(4) -> F-7(4) (586 nm) and D-5(4) -> F-7(3) (622 nm), assigned to possible transitions of Tb3+ ions are seen. The strongest one, observed at 544 nm, due to its probability of both magnetic and electric transitions make the sample emission green. Emissions at 480, 574, 662 and 755 nm were detected for the CaSnO3:Dy3+ and attributed to the transitions from the F-4(9/2) to various energy levels H-6(15/2), H-6(13/2), H-6(11/2) and H-6(9/2)+F-6(11/12) of Dy3+, respectively. CL spectra of Eu doped CaSnO3 reveal that there is a strong emission peak appeared at 615 am due to the electric dipole transition D-5(0) -> F-7(2) (red). Finally, our results show that the rare earth doped CaSnO3 have remarkable potential for applications as optical materials since it exhibits efficient and sharp emission due to rare earth ions. (C) 2015 Elsevier Ltd. All rights reserved.
Characterization, room and low temperature photoluminescence of yttrium aluminium borate activated with Sm3+ions
(Pergamon-Elsevier Science Ltd, 2023) Madkhli, A. Y.; Kaynar, U. H.; Coban, M. B.; Ayvacikli, M.; Canimoglu, A.; Can, N.
In 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.
Comparative studies on thermoluminescence characteristics of non-doped Mg2SiO4 prepared via a solid-state reaction technique and wet-chemical method: An unusual heating rate dependence
(Elsevier Science Sa, 2019) Dogan, T.; Akca, S.; Yuksel, M.; Kucuk, N.; Ayvacikli, M.; Karabulut, Y.; Canimoglu, A.
Magnesium orthosilicate (Mg2SiO4) was synthesized via a traditional solid-state reaction and a wet chemical route. This study primarily reported the thermoluminescence (TL) behavior of Mg2SiO4 host. X-ray diffraction pattern revealed that Mg2SiO4 exhibits orthorhombic structure matched with JCPDS card 900-6398. Dose response, reproducibility and trap parameters of TL glow curves were evaluated to clearly reveal TL features. Two TL glow peaks situated at 81 degrees C and 192 degrees C were monitored at a heating rate of 2 degrees Cs-1. We observed anomalous heating rate effect for the peak centered at 192 degrees C whilst TL intensity of the peak at 81 degrees C decreases with elevating heating rate. Trap depths of the electrons within the trap centers were found to be 1.04 +/- 0.01eV and 1.37 +/- 0.01eV for both methods using peak shape (PS) method. Distribution of trap centers was examined using the T-max - T-stop method and this case indicated that the glow curves consist of single TL peaks. The intensity of TL glow curves exhibited a good linear dose response under total area up to 20 Gy. A comparison of the two preparation techniques revealed that TL characteristics of this phosphor are partly dependent and Mg2SiO4 could be a promising material for dosimetric application. (C) 2019 Elsevier B.V. All rights reserved.
Comparison of thermoluminescence characteristics of undoped and europium doped YAl3(BO3)4 phosphor synthesized by combustion method: Anomalous heating rate, dose response and kinetic analyses
(Pergamon-Elsevier Science Ltd, 2023) Kaynar, Umit H.; Oglakci, M.; Bulcar, K.; Benourdja, S.; Bakr, M.; Ayvacikli, M.; Canimoglu, A.
In this study, undoped and YAl3(BO3)(4) phosphors doped with Eu3+ at varying concentrations (x = 0.5 to 7 wt%) produced by a combustion process have been thoroughly examined by using the X-ray diffraction (XRD) and thermoluminescence (TL) techniques. The crystallized phosphors were confirmed by XRD analysis, and its crystal structure was examined. XRD analyses of the synthesized phosphor is in accordance with ICSD File No 96-152-6006. TL glow curve of undoped sample produced three glow peaks located at 80 degrees C, 240 degrees C, and 360 degrees C with a heating rate of 2 degrees Cs-1 whilst Eu3+ doped one appears at 90 degrees C, 230 degrees C, and 390 degrees C. The undoped example complied with the theory as expected, namely, as the heating rate increased, the TL glow curve shifted towards lower temperatures and decreased in intensity. However, an anomalous change was observed in the sample with Eu3+ additive. The experimental findings from the dose-response of YAl3(BO3)(4):0.5 wt%Eu3+ demonstrate that the intensity of TL provided by the total area under glow curves has an acceptable linearity (r(2):0.999) up to 100 Gy. The intensity of each maximum on the TL glow curve augments proportionally as the heating rate is augmented. Possible reasons of this behaviour are discussed. Various heating rate (VHR) methods (such as Hoogenstraaten's and Booth-Bohun-Parfianovitch) have also been used to estimate kinetic parameters (e.g., energy and frequency factor), which seem to be in good agreement with each other.
Enhancement of luminescence and thermal stability in Eu3+-doped K3Y (BO2)6 with Li+ and Na+ co-doping
(Elsevier, 2024) Kaynar, U. H.; Aydin, H.; Altowyan, A. S.; Hakami, J.; Coban, M. B.; Ayvacikli, M.; Karali, E. Ekdal
Eu3+-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.
Integrating K plus into Eu and Tb doped GdCa 4O(BO3)3: A dual study on photoluminescence and structure
(Elsevier Science Sa, 2024) Altowyan, Abeer S.; Kaynar, U. H.; Hakami, Jabir; Coban, M. B.; Ayvacikli, M.; Aydin, H.; Canimoglu, A.
In 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.
Luminescence characteristics of Dy3+ incorporated zinc borate powders
(Elsevier, 2017) Portakal, Z. G.; Dogan, T.; Yegen, S. Balci; Kucuk, N.; Ayvacikli, M.; Garcia Guine, J.; Canimoglu, A.
We have synthesized powder samples of Dy3+ doped zinc borates by nitric acid method. X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) techniques were utilized to examine the structure and morphological observation of the samples. Luminescence characteristics of the samples were investigated using room temperature (RT) cathodoluminescence (CL) and radioluminescence (RL) measurements under excitation with electron beam and X-rays, respectively. The presence of small amounts of Dy3+ incorporated in the host lattice does not affect the structure of the prepared samples remarkably. The CL and RL spectra showed the characteristic emissions of Dy3+ (magnetic dipole transition of F-4(9/2) -> H-6(11/2) Blue; forced electric dipole transition of F-4(9/2) > H-6(13/2) Yellow; F-4(9/2) -> H-6(1/2) Red; F-4(9/2) -> (H-6(9/2) + H-6(11/2)) infrared). Thermoluminescence (TL) method was also conducted to determine the effects of various concentrations of Dy3+ on the TL properties of ZnB2O4. The TL glow peak of beta irradiated ZnB2O4:Dy3+ phosphors is a well-defined and centered at around 96 degrees C with a constant heating rate of 2 degrees C/s. Initial rise method was employed to observed main TL glow curve for determining the activation energy (E-a) and the frequency factor (s).
Luminescence studies of zinc borates activated with different concentrations of Ce and La under x-ray and electron excitation
(Pergamon-Elsevier Science Ltd, 2017) Kucuk, N.; Ayvacikli, M.; Akca, S.; Yuksel, M.; Garcia Guinea, J.; Karabulut, Y.; Canimoglu, A.
Several ZnB2O4 powder samples having dopants concentrations of 0.1, 0.01, 0.04 wt% Ce and La were prepared using the nitric acid method via the starting oxides. Several complementary methods such as powder X-ray diffraction (XRD), thermal analyses environmental scanning electron microscopy (ESEM), Radioluminescence (RL) and Cathodoluminescence (CL) techniques were used. Unique luminescence properties of Ce doped ZnB2O4 powder samples are reported for the first time. A new luminescence bands appearing in red part of the spectrum and having all the characteristics of Ce3+ were obtained from RL results. Changing the Ce and La concentration of 0.01-0.1 wt% leads to an increase in RL and CL intensities of Ce3+ and La3+ ions and also CL emission spectra of ZnB2O4 show gradual shift towards longer wavelength. When we compare the luminescence intensity of the samples it is seen that Ce doped ZnB2O4 has the highest intense whereas La doped ZnB2O4 has the lowest one. However, emission spectra of both Ce and La doped samples kept unchanged.
Novel Tb3+-Doped LaAl2 B4 O10 phosphors: Structural analysis, luminescent properties, and energy transfer mechanism
(Pergamon-Elsevier Science Ltd, 2024) Kaynar, U. H.; Aydin, H.; Hakami, Jabir; Altowyan, Abeer S.; Coban, M. B.; Ayvacikli, M.; Canimoglu, A.
This 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.
Optical spectroscopy of the Ce-doped multicomponent garnets
(PERGAMON-ELSEVIER SCIENCE LTD, 2016) Canimoglu, A.; Karabulut, Y.; Ayvacikli, M.; Muresan, L. E.; Perhaita, I.; Barbu-Tudoran, L.; Can, N.
Here, we report our results referring to the preparation of Ce doped Y2.22MgGa2Al2SiO12, Y1.93MgAl4SiO12 and Y2.22Gd0.75Ga2Al3O12 using solid state reaction at high temperature. Several complementary methods (i.e. powder x-ray diffraction (XRPD), energy dispersive analysis of X-rays (EDX), scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR)) were studied to examine the effects of the synthesis procedure on the morphology and structure. XRD analyses revealed that all compounds include yttrium aluminate phase with garnet structure. Cathodoluminescence (CL), radioluminescence (RL) and photoluminescence (PL) measurements were carried out for clarification of relationship between host lattice defects and the spectral luminescence emissions. Luminescence emission of phosphors is peaked at 530 nm assigned to 5d-4f transitions of the dopant Ce3+ ions with a broad emission band in 400-700 nm range. Under electron irradiation, the emission spectrum of Ce doped (YGd)(3)Ga2Al3O12 is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312 nm and 624 nm corresponding to transition of P-6(7/2) -> S-8(7/2) and (6)G(J) -> P-6(J) (Gd3+), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation. (C) 2016 Elsevier Ltd. All rights reserved.
Preparation and characterization of Yttrium based luminescence phosphors
(Elsevier Science Bv, 2017) Muresan, L. E.; Ayvacikli, M.; Garcia Guinea, J.; Canimoglu, A.; Karabulut, Y.; Can, N.
Ce doped Yttrium aluminate modified by replacing different molar part of aluminium or gallium (Y(3)Al(5-x)GaxO(12)) and Yttrium silicate phosphors activated with Ce and Tb (Y2SiO5:Ce3+,Tb3+) were synthesized by solid state reaction and a gel combustion method, respectively. X-ray diffraction and Scanning electron microscope (SEM) techniques are used to identify their structures and morphologies. Luminescence characteristics are measured and spectroscopic data confirm that Y2SiO5:Ce3+, Tb3+ phosphors can be effectively excited upon UV excitation light and X-ray irradiation, resulting in intense blue and green emissions, respectively. This energy transfer takes place by means of a non-radiative process inside Ce3+-Tb3+ clusters formed in the host matrix. Tb3+ doped Y2SiO5 yields both blue emission D-5(3) -> F-7(j) (j = 3,4,5,6) and green emission D-5(4) -> F-7(J) (J = 3,4,5,6) of Tb3+. Y(3)Al(5-x)GaxO(12):Ce3+ phosphors exhibit a broad blue emission band originating from allowed 5d-4f transition of the Ce3+ ions under different excitation sources but the broad emission band shifts with increasing of Ga3+ content. This work presents a quantitative understanding of host material's on dopant's luminescence properties and thereby provides an optimization guideline, which is extremely demanding for the development of new luminescent materials. (C) 2017 Elsevier B.V. All rights reserved.
Radioluminescence and photoluminescence characterization of Eu and Tb doped barium stannate phosphor ceramics
(ELSEVIER SCIENCE SA, 2014) Ayvacikli, M.; Canimoglu, A.; Karabulut, Y.; Kotan, Z.; Herval, L. K. S.; de Godoy, M. P. F.; Can, N.
In this paper, we report on structural and optical properties of terbium and europium doped barium stannate phosphors (BaSnO3) synthesised by conventional solid state reaction method. We have studied those materials by using X-ray diffraction (XRD), radioluminescence (RL) and photoluminescence (PL) techniques. XRD patterns confirm that the BaSnO3 sintered at 1400 degrees C exhibit orthorhombic structure and that the Tb3+ and Eu3+ substitution of Ba2+ does not change the structure of the BaSnO3 host. The optical emission spectrum is characterized a broad band centered at 897 nm (1.38 eV), with a high-energy tail approximately 750 nm from the host lattice. Other emission signals that are characteristic of the 3 + oxidation state of rare earth elements were generated by Eu and Tb doping. Luminescence measurements show that the series of emission states D-5(4) -> F-7(6), D-5(4) -> F-7(5), D-5(4) -> F-7(4) and D-5(4) -> F-7(3) corresponding to the typical (4)f -> (4)f infra-configuration forbidden transitions of Tb3+ are appeared and the major emission peak at 540 nm is due to D-5(4) -> F-7(5) transitions of Tb3+. On the other hand, the emission spectrum of Eu doped BaSnO3 phosphor exhibits a series of emission bands, which are attributed to the D-5(0) -> F-7(j) (j = 0-4) transitions of Eu3+ ions. The dominant emission of Eu3+ corresponding to the electric dipole transition D-5(0) -> F-7(2) is located at 613 nm. The sharp emission properties exhibited demonstrate that the BaSnO3 is a suitable host for rare-earth ion doped phosphor material. This work clearly confirms the unusual near infrared (NIR) PL discovered by H. Mizoguchi et al. in BaSnO3 at room temperature. (C) 2013 Elsevier B.V. All rights reserved.
Solid state synthesis of SrAl2O4:Mn2+ co-doped with Nd3+ phosphor and its optical properties
(ELSEVIER SCIENCE BV, 2013) Ayvacikli, M.; Kotan, Z.; Ekdal, E.; Karabulut, Y.; Canimoglu, A.; Garcia Guinea, J.; Can, N.
The optical properties of alkaline earth aluminates doped with rare earth ions have received much attention in the last years and this is due to. their chemical stability, long-afterglow (LAG) phosphorescence and high quantum efficiency. However, there is a lack of understanding about the nature of the rare earth ion trapping sites and the mechanisms which could activate and improve the emission centers in these materials. Therefore a new phosphor material composition, SrAl2O4:Mn2+, co-doped with Nd3+ was synthesized by a traditional solid-state reaction method. The influence of transition metal and rare earth doping on crystal structure and its luminescence properties have been investigated by using X-ray diffraction (XRD), Raman scattering, Photoluminescence (PL) and Radioluminescence (RL). Analysis of the related diffraction patterns has revealed a major phase characteristic of the monoclinic SrAl2O4 compound. Small amounts of the dopants MnCO3 and Nd2O3 have almost no effect on the crsytalline phase composition. Characteristic absorption bands from Nd3+ 4f-4f transitions in the spectra can be assigned to the transitions from the ground state I-4(9/2) to the excited states. The luminescence of Mn2+ activated SrAl2O4 exhibits a broad green emission band from the synthesized phosphor particles under different excitation sources. This corresponds to the spin-forbidden transition of the d-orbital electron associated with the Mn2+ ion. In photo- and radio-luminescence spectra, Nd3+ 4f-4f transition peaks were observed. The emitted radiations for different luminescence techniques were dominated by 560, 870, 1057 and 1335 nm peaks in the visible and NIR regions as a result of I-4(9/2) -> (4)G(7/2) and F-4(3/2) -> I-4(J) (J=9/2, 11/2 and 13/2) transitions of Nd3+ ions, respectively. Multiple emission lines observed at each of these techniques are due to the crystal field splitting of the ground state of the emitting ions. The nature of the emission lines is discussed. (C) 2013 Elsevier B.V. All rights reserved.
Solid state synthesis, characterization and optical properties of Tb doped SrSnO3 phosphor
(ELSEVIER SCIENCE SA, 2013) Kotan, Z.; Ayvacikli, M.; Karabulut, Y.; Garcia-Guinea, J.; Tormo, L.; Canimoglu, A.; Can, N.
In the present study, the structural and optical properties of SrSnO3 doped with Tb ions are reported. Novel SrSnO3:Tb3+ phosphors were conventionally synthesized using a solid state reaction process under a mildly reduced atmosphere (5% H-2 and 95% N-2). The crystal structures, morphologies and optical properties of the resultant materials have been characterised by experimental techniques such as X-ray Diffraction (XRD), Raman spectroscopy (RS), Photoluminescence (PL), Radioluminescence (RL) and Cathodoluminescence coupled to an ESEM (ESEM-CL). The new phosphor material has good crystallization without any impurity phases, which matches with the standard JCPDS files (No. 22-1442) from XRD analysis. The PL, RL and CL measurements taken at room temperature showed that the transitions of D-5(4) to F-7(J) (j = 6, 5, 4, 3) corresponding to the typical 4f -> 4f dipole forbidden intra-configurational transitions of Tb3+ are largely independent of the host material. The green emissions of the D-5(4) -> F-7(5) magnetic dipole transition at similar to 540 nm are predominant for three types of luminescence. PL emission spectra recorded in the temperature range from 10 K to 300 K were influenced by temperature. We report anomalies in the PL spectra of SrSnO3:Tb3+ compatible with a structural phase transition at 260 K while simultaneously exciting and cooling the sample. This work clearly confirms the existence of a phase transition discovered by Singh et al. in SrSnO3 at 270 K. (C) 2013 Elsevier B.V. All rights reserved.
Structural and luminescence effects of Ga co-doping on Ce-doped yttrium aluminate based phosphors
(ELSEVIER SCIENCE SA, 2016) Ayvacikli, M.; Canimoglu, A.; Muresan, L. E.; Tudoran, L. Barbu; Garcia Guinea, J.; Karabulut, Y.; Can, N.
Herein, we primarily focus on luminescence spectrum measurements of various types of green emitting yttrium aluminate phosphors modified with gallium (Y3Al5-xGaxO12) synthesised by solid state reaction. The luminescent emission of samples depends on sample temperature and excitation radiation such as incident X-ray, electron and laser beam. Here, we measured radioluminescence (RL), cathodoluminescence (CL), photoluminescence (PL) along with XRD in order to clarify relationship between lattice defects and the spectral luminescence emissions. The RL and CL spectra of YAG:Ce exhibit an emission band ranging from 300 to 450 nm related to Y-Al antisite defects. The broad emission band of garnet phosphors is shifted from 526 nm to 498 nm with increasing of Ga3+ content, while full width at half maximum (FWHM) of the band tends to be greater than the width of unmodified YAG: Ce garnet. Deconvolution of the spectrum reveals that three emission bands centred at 139, 234 and 294 degrees C occur in aluminate host garnets. (C) 2016 Elsevier B.V. All rights reserved.
Synthesis and enhanced photoluminescence of the BaSiF6:Dy3+ phosphors by Li+ doping via combustion method
(Elsevier, 2022) Souadi, G.; Kaynar, U. H.; Ayvacikli, M.; Canimoglu, A.; Can, N.
Undoped BaSiF6, Dy3+ doped BaSiF6, and Dy3+, Li+ co-doped BaSiF6 phosphors were synthesized through a gelcombustion method. The prepared samples were characterized by powder x-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive x-ray spectroscopy (EDS), and photoluminescence (PL) techniques. The XRD data revealed that both the Dy3+ doped and Li+ co-doped BaSiF6 phosphors exhibited a single-phase structure belonging to the space group R (3m) over bar which matched well with the standard JCPDS files (No. 002-6613). FTIR spectra showed absorption bands at 3417 cm -1 , 1640 cm(-1), and 1620 cm(-1) corresponding to water molecules. EDS analysis confirmed the chemical composition of the prepared samples. The PL emission spectra of BaSiF6:Dy3+ by different co-doping concentrations of Li+ exhibited prominent emission peaks at 490 nm, 572 nm, 672 nm and 758 nm. The incorporation of Li+ is beneficial for enhancing the photoluminescence intensity. The optimum Li+ amount was 8% for BaSiF6:Dy3+ and then started to decrease. The enhancement could be due to the occurrence of oxygen vacancies due to the incorporation of Li+ ions. The x = 0.301 and y = 0.361 coordinates of this phosphor with varying Li+ dopant concentration determined by the Commission Internationale de l'Eclairage (CIE - 1931) were in the white range. The present work demonstrates how a simple and effective method can be used to prepare novel nanophosphors for applications in the field of visible light emitting devices with enhanced white emission.
Synthesis and Luminescence Properties of Trivalent Rare-Earth Element-Doped Calcium Stannate Phosphors
(TAYLOR & FRANCIS INC, 2014) Karabulut, Y.; Ayvacikli, M.; Canimoglu, A.; Guinea, J. Garcia; Kotan, Z.; Ekdal, E.; Can, N.
The phosphors of calcium stannate activated with individual trivalent rare-earth element (REE) ions (Neodymium III, Europium III, Terbium III, Dysprosium III, and Samarium III) were synthesized by high-temperature solid-state reaction (SSR), and their characterization and luminescent properties were investigated. The crystal structures and morphologies of the resultant materials were well characterized by experimental techniques such as X-ray powder diffraction (XRD) and environmental scanning electron microscopy (ESEM). The XRD results display that the rare-earths substitution of Calcium II does not change the structure of calcium stannate host. Obviously, the ESEM image exhibits that phosphors aggregate and their particles with irregular shape exist. The calcined powders of the Europium III, Neodymium III, Samarium III, Dysprosium III, and Terbium III ions doped in calcium stannate exhibits bright red, reddish orange, yellowish, orange white, and green light, respectively. Although there is some intrinsic emission ranging from UV to near-infrared (NIR) due to the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the trivalent rare-earth states. The emission spectrum from undoped-calcium stannate phosphor is characterized by two broad bands centered at similar to 800 and similar to 950nm. The shapes of the emission bands are different for each dopant. The sharp emission properties show that the calcium stannate is a suitable host for rare-earth ion-doped phosphor material. Furthermore the influence of different rare-earth dopants, that is, Europium III, Neodymium III, Samarium III, Dysprosium III, and Terbium III, on thermally stimulated luminescence (TSL) of calcium stannate phosphor under the beta irradiation was discussed. Among these trivalent rare-earth-doped phosphors samarium-doped material showed maximum TSL sensitivity with favorable glow curve shape.
Synthesis and photoluminescence characteristics of a novel Eu and Tb doped Li2MoO4 phosphor
(Pergamon-Elsevier Science Ltd, 2021) Souadi, G.; Kaynar, U. H.; Ayvacikli, M.; Coban, M. B.; Oglakci, M.; Canimoglu, A.; Can, N.
Li2MoO4: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.

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