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Cathodoluminescence Response From Sanidine Feldspar
(TAYLOR & FRANCIS INC, 2013) Karabulut, Y.; Canimoglu, A.; Can, N.
In the present study, cathodoluminescence (CL) providing information about surface rather than bulk material reveals blue and red emissions within the sanidine feldspar from the Eifel Mountains, Germany. The emission line occurring in the blue region at about 450nm reflects Al-O--Al structural defects, although distribution maps of the major elements, including Si, Al, and K, do not display a clear correlation with the CL properties of the sanidine feldspar. Dominant emission being in the longer-visible wavelength region (red region) approximate to 730nm is assumed to be caused by Fe3+ activation attributed to Fe3+-Al3+ substitution. Much less is known about the spectral characteristic of the feldspar CL emission, and the application of an older luminescence technique yields encouraging results for the practical application of the feldspar identification.
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.
Characterisation and luminescence studies of Tm and Na doped magnesium borate phosphors
(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Ekdal, E.; Garcia Guinea, J.; Karabulut, Y.; Canimoglu, A.; Harmansah, C.; Jorge, A.; 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 350 nm 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, 475 nm due to the respective transitions of D-1(2)-> H-3(6),D-1(2)-> F-3(4) and (1)G(4)-> H-3(6) 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. (C) 2015 Elsevier Ltd. All rights reserved.
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.
Doping Sm3+ into ZnB2O4 phosphors and their structural and cathodoluminescence properties
(ELSEVIER SCIENCE SA, 2018) Kucuk, N.; Bulcar, K.; Dogan, T.; Garcia Guinea, J.; Portakal, Z. G.; Karabulut, Y.; Can, N.
In this study, ZnB2O4:xSm(3+) (0.01 <= x <= 0.05 mol) powder phosphors have been synthesized by low temperature chemical synthesis method. The structure and morphological observation of the phosphor samples were systematically 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#39-1126). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). When excited with electron beam, CL spectral measurements of scrutinized phosphors exhibit orange-red luminescence at 572 nm, 606 nm and 658 nm due to various transition from ground state to H-6(5/2),H-6(7/2) and (4)G(5/2) states, respectively. The transition (4)G(5/2) -> H-6(7/2) located at 606 nm can occur as hypersensitive transition having the selection rule Delta J = +/- 1. The observed peaks are in the region of yellow reddish light of Sm3+. Experimental results verify that the optimum Sm3+ content in terms of intense luminescence for this series of phosphors was 2%. Beyond 2% of Sm3+ ions concentration, luminescence quenching occurs due to an enhanced probability of the energy transfer from one Sm3+ to another that matches in energy via cross-relaxation and dipole-dipole interactions according to Dexter theory. A suitable energy transfer model between two adjacent Sm3+ ions in the ZnB2O4 phosphors was accomplished by the electric dipole-dipole interaction. The critical transfer distance (R-c) for non-radiative energy transfer was found to be 21.52 angstrom at 2 mol % Sm3+ doped ZnB2O4. Additionally, thermoluminescence (TL) glow curves of undoped and Sm activated ZnB2O4 under beta irradiation of 10 Gy are also discussed here. (C) 2018 Elsevier B.V. All rights reserved.
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.
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.
Luminescent, Structural, and Thermal Properties of the Unusual "Anatolian" Diaspore (Zultanite) from Turkey
(TAYLOR & FRANCIS INC, 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 Mugla 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 degrees C-500 degrees 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 E-2 ->(4)A(2) transitions of substitutional Cr3+ luminescent centers in positions of Al3+ in sixfold coordination.
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.
Strong Visible and Near-Infrared Cathodoluminescence in Alkali Feldspar
(TAYLOR & 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 40-293K 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 similar to 460nm could be associated with Al-O--Al or Ti impurity centers, yellow emission similar to 560nm could be associated with the presence of the centers such as radiation-induced defect centers, and similar to 756nm emission could be associated with the Fe3+ impurity center on T-1 and T-2 sites. The consequence of their association is to produce different luminescence properties such as intensity, peak wavelength, and band shape.
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 influence of ultrasonic treatment on luminescence of Mn incorporated ZnS nanoparticles
(Elsevier Science Bv, 2017) Cadis, A. -I.; Muresan, L. E.; Perhaita, I.; Munteanu, V.; Karabulut, Y.; Garcia Guinea, J.; Canimoglu, A.
Manganese (Mn) doping of ZnS phosphors was achieved by precipitation method using different ultrasound (US) maturation times. The structural and luminescence properties of the samples were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), photoluminescence (PL), and cathodoluminescence (CL). The real amount of manganese incorporated in ZnS lattice was calculated based on ICP-OES results. According with XRD patterns, the phase structure of ZnS:Mn samples is cubic. EDS spectra reveal deviations of the Mn dopant concentration from the target composition. Both 300 K PL and CL emission spectra of the Mn doped ZnS phosphors display intense orange emission at 590 and 600 nm, respectively, which is characteristic emission of Mn ion corresponding to a T-4(1) -> (6)A(1) transition. Both PL and CL spectra confirmed manganese is substitutionally incorporated into the ZnS host as Mn2+. However, it is suggested that the origin of broad blue emission around 400 nm appeared in CL is due to the radiative recombination at deep level defect states in the ZnS. The ultrasound treatment at first enhances the luminescent intensity by similar to 3 times in comparison with samples prepared by classical way. This study gives rise to an optimization guideline, which is extremely demanded for the development of new luminescent materials. (C) 2017 Elsevier B.V. All rights reserved.
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 Dy incorporated MoO3 phosphor: Suppression concentration quenching
(Pergamon-Elsevier Science Ltd, 2020) Ayvacikli, M.; Kaynar, Umit 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 F-4(9/2) -> H-6(15/2), F-4(9/2) -> H-6(13/2) and F-4(9/2) -> H-6(11/2), 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.
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.
Tunable luminescence of broadband-excited and narrow line green emitting Y2SiO5:Ce3+, Tb3+ phosphor
(ELSEVIER SCIENCE SA, 2016) Muresan, L. E.; Karabulut, Y.; Cadis, A. I.; Perhaita, I.; Canimoglu, A.; Garcia Guinea, J.; Can, N.
Cerium and terbium activated white emitting yttrium silicate phosphors (Y-2-x-yCe(x)Tb(y)SiO(5)) having average size between 96 and 123 nm were synthesised by a gel-combustion, and their phase and crystal structures, morphologies and ultraviolet (UV)-visible spectroscopic properties were studied. All rare earth doped yttrium silicate (YSO) phosphors are well crystallized powders containing only monoclinic X2-Y2SiO5 phase. No significant changes in the cell parameters were observed with increasing of Tb amount as ionic radii of Tb3+ (0.923 angstrom) and Y3+ (0.9 angstrom) have almost the same. Under different excitations, YSO:Ce3+ exhibits blue emission due to the 5d-4f transitions of Ce3+ ions. The series of emission states at different wavelengths of YSO:Tb3+ associated to f-f transition of Tb3+ ion were detected from luminescence measurements. The emission observed at 544 nm (green) corresponding to D-5(4) -> F-7(5) of Tb3+ is strongest one. Incorporation of variable amounts of Tb3+ in the YSO host lattice determines the modification of emission colour from blue through light blue and eventually to bluish green. A possible energy transfer mechanism taking place from Ce3+ to Tb3+ was also discussed in terms of excitation and emission spectra. (C) 2015 Elsevier B.V. All rights reserved.

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