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Öğe Eu3+ and Dy3+ doped La2MoO6 and La2Mo2O9 phosphors: Synthesis and luminescence properties(Pergamon-Elsevier Science Ltd, 2020) Kaynar, Umit H.; Kaynar, S. Cam; Alajlani, Y.; Ayvacikli, M.; Karali, E.; Karabulut, Y.; 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 (F-4(9/2) -> H-6(15/2)) and 572 nm (F-4(9/2) -> H-6(13/2)), and also Eu doped samples showed a sharp emission peaks at 612 and 619 nm (D-5(0) -> F-7(2)) 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.Öğe Luminescence of dysprosium doped strontium aluminate phosphors by codoping with manganese ion(Elsevier Science Sa, 2014) Karabulut, Y.; Canimoglu, A.; Kotan, Z.; Akyuz, O.; Ekdal, E.The authors report here the luminescence properties of strontium aluminate doped with dysprosium and manganese. The dysprosium, manganese co-doped powders were prepared by a solid state reaction at temperatures at 1600 degrees C under H-2 (15%)-Ar (85%) atmosphere. The dysprosium, manganese co-doped strontium aluminate phosphors have the monoclinic structure with lattice parameters a approximate to 8.440 angstrom, b approximate to 8.821 angstrom, c approximate to 5.157 angstrom and beta approximate to 93.4 degrees. The characteristic (4)F9/2 -> H-6(15/2) (blue), F-4(9/2) -> H-6(13/2) (yellow), F-4(9/2) -> H-6(11/2) (red) and F-4(9/2) -> H-6(9/2) (NIR) transitions of Dy3+ for different luminescence techniques (radioluminescence, photoluminescence and cathodoluminescence) were detected in the emission spectra at the room temperature. The luminescence of Mn2+ co-doped SrAl2O4:Dy3+ exhibits a broad greenorange emission band (T-4(1) -> (6)A(1) transition) 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. 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.Öğe 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.; Guinea, J. Garcia; Karali, T.; 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.Öğe 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.; Galvao Gobato, Y.; Henini, M.; 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.Öğe 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.; Khatab, A.; Henini, M.; 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.Öğe 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.; Karali, T.; 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.Öğe 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.; Jorge, A.; Karali, T.; 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.Öğe 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.; Akyuz, O.; 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.Öğe Thermoluminescence studies of Nd doped Bi4Ge3O12 crystals irradiated by UV and beta sources(Pergamon-Elsevier Science Ltd, 2016) Karabulut, Y.; Canimoglu, A.; Ekdal, E.; Ayvacikli, M.; Can, N.; Karali, T.Thermoluminescence (TL) glow curves of pure and rare earth doped bismuth germanate (BGO) were investigated under UV and beta radiation. The glow curves of pure BGO crystal present different patterns for both kinds of radiation. The TL glow curves of BGO crystals doped with Nd ions are similar to that of pure BGO under UV radiation. The kinetic parameters, kinetic order (b), activation energy (E) and frequency factor (s) of the TL glow curves of pure BGO crystal have been determined by peak shape method. Activation energies of 3 peaks obtained by PS were found to be 1.81, 1.15 and 1.78, respectively. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Visible to infrared low temperature photoluminescence of rare earth doped bismuth germanate crystals(Pergamon-Elsevier Science Ltd, 2016) Canimoglu, A.; Ayvacikli, M.; Karabulut, Y.; Karali, T.; Can, N.In this paper, the influence of a series of rare earth (Eu, Tm, Nd) and Cr ion doping on the optical properties of BGO was investigated by means of photoluminescence (PL) from visible to IR region in the 10-300 K temperature range using different types of detectors, namely, photomultiplier tube (PMT), InGaAs (IGA), and Si. Several samples were investigated having dopants concentrations of 03 wt%Nd, 0.4 wt%Tm, 0.06 wt% Cr and 3 ppm Eu. The PL spectra of the samples showed different luminescence behaviour which is assigned to the 4f intra shell transition from rare earth ions. The temperature dependence of the PL from rare earth doped BGO crystals is also examined. (C) 2016 Elsevier Ltd. All rights reserved.
