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Browsing by Author "Canimoglu A."

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Room and low temperature luminescence properties of CaSO4:Dy,Tm codoped with Li
(Elsevier B.V., 2009) Can N.; Karali T.; Wang Y.; Townsend P.D.; Prokic M.; Canimoglu A.
Rare earths, especially Dy or Tm doped CaSO4 phosphors are actively studied. They have high sensitivity, a large dynamic range, thermal stability and ease of preparation. Nevertheless, they can be enhanced by inclusion of lithium and this study reports some effects of lithium co-dopant on the TL and radioluminescence (RL) emissions of two TL phosphors. Addition of Li as a co-dopant ion was made either during chemical preparation of the phosphors, or as a binder component mixed with the basic phosphors matrix during the process of pressing and sintering the TLD pellets.
Cathodoluminescence response from rare earth doped Bi4Ge 3O12
(Elsevier B.V., 2009) Kibar R.; Çetin A.; Tuncer Y.; Uysal S.; Townsend P.D.; Canimoglu A.; Karali T.; Can N.
Room and low temperature cathodoluminescence (CL) of rare earth doped Bi4Ge3O12 (BGO) has been recorded. Luminescence signals noted in the wavelength range (300 - 800 nm) include intrinsic broad emission bands and signals related to Eu3+, Nd3+, and Tm3+. CL measurements made on Bi4Ge3O 12 (BGO) doped with rare earth ions are reported for the temperature range 40 to 300 K with different CL excitation modulation frequencies. Dopant levels used in the present study are 1.1, 0.4, and 0.3 wt% Nd, 0.4 wt% Tm and 3 ppm Eu. All dopant levels exhibited different CL spectra with evidence for lines due to the rare-earth dopants intra-4f transitions. The temperature dependence of the intensity of the emission band is discussed.
Solid state synthesis, characterization and optical properties of Tb doped SrSnO3 phosphor
(Elsevier Ltd, 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 SrSnO 3 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%H2 and 95%N2). 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 5D4 to 7FJ (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 5D4?7F5 magnetic dipole transition at 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. © 2013 Elsevier B.V. All rights reserved.
Solid state synthesis of SrAl2O4:Mn2+ co-doped with Nd3+ phosphor and its optical properties
(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 SrAl2O 4 compound. Small amounts of the dopants MnCO3 and Nd 2O3 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 4I9/2 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 4I9/2→4G7/2 and 4F3/2→4IJ (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. © 2013 Elsevier B.V.
Synthesis and luminescence properties of trivalent rare-earth element-doped calcium stannate phosphors
(Taylor and Francis Inc., 2014) Karabulut Y.; Ayvacikli M.; Canimoglu A.; Guinea J.G.; 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 ∼800 and ∼950 nm. 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. © 2014 Copyright Taylor & Francis Group, LLC.
Strong visible and near-infrared cathodoluminescence in alkali feldspar
(Taylor and Francis Inc., 2014) Karabulut Y.; Canimoglu A.
In this study, cathodoluminescence (CL) spectroscopy at direct current and alternating current under the sample temperature condition of 40-293 K using different modulation frequencies is presented for alkali feldspar from the Dartmoor granite (UK). These feldspars contain strain-controlled lamellar crypto-and microperthites that are cross-cut by strain-free deuteric microperthites. The CL spectra of the alkali feldspar at room and low temperature confirm that the observed emission peaked at ∼460 nm could be associated with Al-O--Al or Ti impurity centers, yellow emission ∼560 nm could be associated with the presence of the centers such as radiation-induced defect centers, and ∼756 nm emission could be associated with the Fe3+ impurity center on T1 and T2 sites. The consequence of their association is to produce different luminescence properties such as intensity, peak wavelength, and band shape. © 2014 Copyright Taylor & Francis Group, LLC.
Luminescent, structural, and thermal properties of the unusual "anatolian" diaspore (zultanite) from Turkey
(2014) Canimoglu A.; Garcia-Guinea J.; Correcher V.; Karabulut Y.; Tuncer Y.; Can N.
Results are presented for the cathodoluminescence (CL) probe of an environmental scanning electron microscopy (ESEM) with an energy-dispersive spectrometry analyzer (EDS), thermoluminescence (TL), thermo X-ray diffraction in situ (TXRD), and simultaneous differential thermal analysis and thermogravimetric analysis (DTA/TGA) techniques of gem-quality zultanite samples collected from the Muǧla region of southwest Turkey. Micro-Raman measurements were also performed on different zultanite orientations and preheated aliquots to study the spectral phase transition diaspore-corundum also detected by the other thermal techniques in the 450°C-500°C thermal range. The thermal phenomena of TL are synchronous with this dehydroxylation process, involving consecutive breaking-linking bonds of Al-O, Cr-O, Fe-O, Al-OH, Cr-OH, and Fe-OH, including the formation of hydrolyzed ions such, and and redox reactions. Assuming that zultanite oxygen atoms are distributed as a hexagonal close packed layer, the experimental spectrum CL of zultanite is characteristic of the 2E → 4A2 transitions of substitutional Cr3+ luminescent centers in positions of Al 3+ in sixfold coordination. © 2014 Copyright Taylor and Francis Group, LLC.
Radioluminescence and photoluminescence characterization of Eu and Tb doped barium stannate phosphor ceramics
(2014) Ayvacikli M.; Canimoglu A.; Karabulut Y.; Kotan Z.; Herval L.K.S.; De Godoy M.P.F.; Galvão 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 C exhibit orthorhombic structure and that the Tb3+ and Eu3+ substitution of Ba2+ does not change the structure of the BaSnO 3 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 5D4 → 7F6, 5D 4 → 7F5, 5D4 → 7F4 and 5D4 → 7F3 corresponding to the typical 4f → 4f infra-configuration forbidden transitions of Tb3+ are appeared and the major emission peak at 540 nm is due to 5D4 → 7F5 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 5D0 → 7Fj (j = 0-4) transitions of Eu3+ ions. The dominant emission of Eu3+ corresponding to the electric dipole transition 5D0 → 7F2 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. © 2014 Elsevier B.V. All rights reserved.
Luminescence of dysprosium doped strontium aluminate phosphors by codoping with manganese ion
(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 C under H 2 (15%)-Ar (85%) atmosphere. The dysprosium, manganese co-doped strontium aluminate phosphors have the monoclinic structure with lattice parameters a ≈ 8.440 Å, b ≈ 8.821 Å, c ≈ 5.157 Å and β ≈ 93.4. The characteristic 4F9/2 → 6H15/2 (blue), 4F9/2 → 6H13/2 (yellow), 4F9/2 → 6H11/2 (red) and 4F9/2 → 6H9/2 (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 SrAl2O 4:Dy3+ exhibits a broad green-orange emission band ( 4T1 → 6A1 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. © 2013 Elsevier B.V. All rights reserved.
Cathodoluminescence and Raman characteristics of CaSO4:Tm3+, Cu phosphor
(Elsevier, 2015) Ekdal E.; Guinea J.G.; Kelemen A.; Ayvacikli M.; Canimoglu A.; Jorge A.; Karali T.; 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 ν1SO4 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 3P0→3H4, 1D2→3H6, 1D2→3F4 were clearly identified. The study is novel as no such CL-ESEM data are available for this doped compound. © 2015 Elsevier B.V. All rights reserved.
Visible to infrared low temperature luminescence of Er3+, Nd3+ and Sm3+ in CaSnO3 phosphors
(Elsevier Ltd, 2015) Orsi Gordo V.; Tuncer Arslanli Y.; Canimoglu A.; Ayvacikli M.; Galvão Gobato Y.; Henini M.; Can N.
Novel stannate phosphor, orthorhombic CaSnO3 phosphors doped with Er3+, Nd3+ and Sm3+ have been synthesized by a conventional solid-state method under N2+H2 gas flow. Visible and near-infrared photoluminescence (PL) properties were investigated as function of laser power and temperature. It was observed that all dopant ions are well incorporated in CaSnO3 and are responsible for the optical emission in the temperature range of 10-300K. PL peaks at 490, 546, 656, 696, 894, 1065, and 1344nm were observed for the CaSnO3:Nd3+ phosphor and associated to f-f transition of Nd3+ ion. Emissions at 564, 600-607, 646-656 and 714nm were detected for the CaSnO3:Sm3+. The strongest one, observed at 600nm, was associated to 4G5/2→6H7/2 of Sm3. Emission lines at 528, 548, 662 at 852nm were also seen for CaSnO3:Er3+ and correspond to Er3+ intra-4fn shell transitions. In addition, at low temperatures, a stark splitting of the 4f electron energy levels of the Er3+ ions were observed in infrared region (1520-1558nm) and assigned to the transition between the 4I13/2 state and the 4I15/2 state. Finally, our results show that the rare earth doped CaSnO3 has remarkable potential for applications as optical material since it exhibits efficient and sharp emissions due to rare earth ions. © 2015 Elsevier Ltd.
Catholuminescence properties of rare earth doped CaSnO3 phosphor
(Elsevier 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°C exhibits orthorhombic structure. The evidence and rationale for two strong broad emission bands appeared at 360 and 780nm for undoped CaSnO3 are presented. The CL measurements exhibit that the 4f-4f emissions from 5D4→7F6 (490nm), 5D4 →7F5 (544nm), 5D4 →7F4 (586nm) and 5D4 →7F3 (622nm), assigned to possible transitions of Tb3+ ions are seen. The strongest one, observed at 544nm, due to its probability of both magnetic and electric transitions make the sample emission green. Emissions at 480, 574, 662 and 755nm were detected for the CaSnO3:Dy3+ and attributed to the transitions from the 4F9/2 to various energy levels 6H15/2, 6H13/2, 6H11/2 and 6H9/2+6F11/2 of Dy3+, respectively. CL spectra of Eu doped CaSnO3 reveal that there is a strong emission peak appeared at 615nm due to the electric dipole transition 5D0→7F2 (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. © 2015 Elsevier Ltd.
Studies on luminescence from a cerium-doped strontium stannate phosphor
(John Wiley and Sons Ltd, 2015) Karabulut Y.; Ayvacikli M.; Canimoglu A.; Garcia Guinea J.; Can N.
The crystal structure and morphology of Ce3+-doped SrSnO3 materials prepared using the solid-state reaction method were extensively characterized using experimental techniques. X-Ray diffraction results show that the cerium substitution of strontium does not change the structure of the strontium stannate. Raman spectroscopy was used to investigate the microstructures and lattice vibrations. Environmental scanning electron microscopy images showed that phosphors aggregate and their particles form irregular shapes. SrSnO3 exhibits an intense green emission with a broad band originating from the 5d1 → 4f1 transition of cerium. It was observed that, after exposure to beta-irradiation, the glow curve of this material has two broad thermoluminescence peaks, one centered at ∼ 127C and the other at ∼ 245C for a heating rate of 5 K/s. The kinetic parameters, which include the frequency factor and the activation energy of the material, were calculated using Chen's method, after beta-irradiation. The fading and reusability of the phosphor were also studied and it was found that the phosphor is suitable for radiation dosimetry. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.
Characterisation and luminescence studies of Tm and Na doped magnesium borate phosphors
(Elsevier Ltd, 2015) Ekdal E.; Garcia Guinea J.; Karabulut Y.; Canimoglu A.; Harmansah C.; Jorge A.; Karali T.; Can N.
In this study, structural and luminescence properties of magnesium borate of the form MgB4O7 doped with Tm and Na were investigated by X-ray diffraction (XRD), Raman spectroscopy and cathodoluminescence (CL). The morphologies of the synthetised compounds exhibit clustered granules and road-like materials. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect is discussed. The CL spectra of undoped MgB4O7 shows a broad band emission centred around 350nm which is postulated to be produced by self-trapped excitons and some other defects. From the CL emission spectrum, main emission bands centred at 360, 455, 475nm due to the respective transitions of 1D2→3H6,1D2→3F4 and 1G4→3H6 suggest the presence of Tm3+ ion in MgB4O7 lattice site. CL mechanism was proposed to explain the observed phenomena which are valuable in possibility of the developing new luminescent materials for different applications. In addition, the experimental Raman spectrum of doped and undoped MgB4O7 were reported and discussed. © 2015 Elsevier Ltd.
Thermoluminescence studies of Nd doped Bi4Ge3O12 crystals irradiated by UV and beta sources
(Elsevier 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. © 2016 Elsevier Ltd.
Broadband luminescence of Cu nanoparticles fabricated in SiO2 by ion implantation
(Elsevier Ltd, 2016) Nguyen T.K.; Le K.Q.; Canimoglu A.; Can N.
In this study, we investigate optical properties of metal nanoparticle crystals fabricated by implanting copper (Cu) ions into single silica (SiO2) crystals with 400 keV at various ion doses. The Cu implanted SiO2 (SiO2:Cu) crystal produces a broadband luminescence emission, ranging from blue to yellow, and having a blue luminescence peak at 546 nm. Such anomalous luminescence emission bands suggest that the ion implantation may give rise to aggregation of Cu nanoparticles in the host matrix. The boundary element method-based modelling of a given Cu nanoparticle aggregation was employed to justify the broadband luminescence emission. Formation of Cu nanoparticles in SiO2 is predicted through their optical absorption data. The experimental results are compared with results of Mie calculations and we observe that the higher ion dose produces the larger particle size. © 2016 Elsevier Ltd
Optical spectroscopy of the Ce-doped multicomponent garnets
(Elsevier Ltd, 2016) Canimoglu A.; Karabulut Y.; Ayvacikli M.; Muresan L.E.; Perhaita I.; Barbu-Tudoran L.; Garcia Guinea J.; 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)3Ga2Al3O12 is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312 nm and 624 nm corresponding to transition of 6P7/2 →8S7/2 and 6GJ→6PJ (Gd3+), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation. © 2016 Elsevier Ltd.
Study of luminescence of Mn-doped CaB4O7 prepared by wet chemical method
(Elsevier Ltd, 2016) Oguz K.F.; Ekdal E.; Aslani M.A.A.; Canimoglu A.; Garcia Guinea J.; Can N.; Karali T.
In this study, manganese (Mn) doped Calcium Tetraborate (CaB4O7) samples were prepared by the wet chemical method. Under beta irradiated, CaB4O7:Mn showed thermally stimulated luminescence (TSL) glow peaks at approximately 85 °C and 220 °C with a heating rate of 5 °C/s. Peak shape (PS) and various heating rates (VHR) methods were applied for determining the trap parameters such as order of kinetic (b), activation energy (E) and frequency factor (s). The results indicate that the main dosimetric peak of CaB4O7:Mn follows the second-order kinetic model. The thermal fading ratio of the material is around 15% at the end of one month period of storage. The results of the TL studies carried out on the CaB4O7:Mn dosimeter revealed that it has high sensitivity, which makes it very valuable in various dosimetric applications like space, medical, personal dosimetry and dating. Radioluminescence (RL) of CaB4O7:Mn was also studied. It is shown that the RL spectrum contains a wide band centered at 530 nm assigned to Mn2+ ion emission. A broad band emission feature peaked at 350 nm assigned to the non-bridging oxygen hole center (NBOHC) is also discussed and a model is proposed to explain this broad band feature. © 2016 Elsevier B.V. All rights reserved.
Visible to infrared low temperature photoluminescence of rare earth doped bismuth germanate crystals
(Elsevier 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 0.3 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. © 2016 Elsevier Ltd.
Structural and luminescence effects of Ga co-doping on Ce-doped yttrium aluminate based phosphors
(Elsevier Ltd, 2016) Ayvacikli M.; Canimoglu A.; Muresan L.E.; Barbu Tudoran L.; 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 YAl 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°C occur in aluminate host garnets. © 2016 Elsevier B.V. All rights reserved.

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