MCBÜ Açıkerişim Sistemi :: Browsing by Author "Ege A."

Browsing by Author "Ege A."

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Kinetic characterization of MgB4O7: Dy,Na thermoluminescent phosphor
(Institute of Physics Publishing, 2006) Karsu E.C.; Gökçe M.; Ege A.; Karali T.; Can N.; Prokic M.
Dosimeters of MgB4O7 doped with Dy and Na have many valuable features such as high sensitivity, tissue equivalence, low fading, non-requirement of annealing and insensitivity to light. Thermoluminescence studies of Dy and Na doped MgB4O7 samples showed that a glow emission peaked at about 195 °C. In this study, the trapping parameters associated with the main dosimetric peak, namely at 195 °C, of Dy and Na doped MgB4O7 are investigated. Isothermal luminescence decay, glow curve shape, initial rise (linear regression) and Tm - Tstop methods were used. We report the results on the kinetic behaviour and activation energy determination of the peak occurring at 195 °C with a moderate heating rate of 2 °C s-1. The average activation energies obtained by the isothermal luminescence decay method, glow curve shape method and initial rise method are calculated to be 1.03 eV, 0.95 eV and 0.89 eV, respectively. The methods mentioned above indicate that the dosimetric peak may consist of one or more second-order components. The frequency factors obtained by the three methods are 3.5 × 1010 s-1, 1.6 × 109 s-1 and 3.4 × 108 s-1, respectively. Results obtained using all these methods are compared and discussed. © 2006 IOP Publishing Ltd.
Effect of heating rate on kinetic parameters of β-irradiated Li 2B4O7:Cu,Ag,P in TSL measurements
(Institute of Physics Publishing, 2007) Ege A.; Ekdal E.; Karali T.; Can N.; Prokić M.
The effect of heating rate on the thermally stimulated luminescence (TSL) emission due to the temperature lag (TLA) between the TSL material and the heating element has been investigated using Li2B4O 7:Cu,Ag,P dosimetric materials. The TLA becomes significant when the material is heated at high heating rates. TSL glow curves of Li 2B4O7:Cu,Ag,P material showed two main peaks after β-irradiation. The kinetic parameters, namely activation energy (E) and frequency factor (s) associated with the high temperature main peak of Li2B4O7:Cu,Ag,P were determined using the method of various heating rates (VHR), in which heating rates from 1 to 40 K s-1 were used. It is assumed that non-ideal heat transfer between the heater and the material may cause significant inconsistency of kinetic parameter values obtained with different methods. The effect of TLA on kinetic parameters of the dosimeter was examined. © 2007 IOP Publishing Ltd.
Annual dose measurement for luminescence dating in Salihli, Turkey
(2009) Ege A.; Ekdal Tekin E.; Karali T.; Can N.
Determination of the annual dose level of an area is one of the most important parameters in calculating the geological and archaeological age of the sample using luminescence techniques. Therefore, the concentrations of the natural radionuclides in soils and samples have to be determined since naturally occurring radioactivity provides a major contribution to the annual dose. In this study, the annual dose level of Salihli, Turkey, was determined with 2 different methods: an indirect method that involves the measurement of the concentrations of the naturally occurring radionuclides and a direct method in which thermoluminescence dosimeters (TLDs) are used. The concentrations of the natural radionuclides in soil samples were determined using HPGe γ-ray spectrometry. In the direct method, Al2O3:C thermoluminescence dosimeters were used. These dosimeters were chosen because of their high sensitivity and usability in dating studies. The results obtained from both methods were compared and discussed. © TÜBİTAK.
Reply to comments on 'effect of heating rate on kinetic parameters of β-irradiated Li2B4O7:Cu,Ag,P in TSL measurements'
(2009) Ege A.; Tekin E.; Can N.; Prokić M.
We appreciate the opportunity to respond to comments regarding the paper published by Ege et al (2007 Effect of heating rate on kinetic parameters of β-irradiated Li2B4O7:Cu,Ag,P in TSL measurements Meas. Sci. Technol. 18 889). We would like to thank the authors for taking the time to tell us about their opinion, but unfortunately we do not agree with them completely. In the article presented by Kumar and Chourasiya some comment is advanced to the analysis of the glow curves measured with different heating rates, presented in our recent study. According to our study, the area under the glow curve decreases with increasing heating rate in TL-temperature plots due to the quenching effects. Contrary to this, Kumar and Chourasiya suggest that this decrease is due to the normalization process. Here we hope to clarify any confusion regarding our published study. © 2009 IOP Publishing Ltd.
Radioluminescence of SrAl2O4:Ln3+ (Ln = Eu, Sm, Dy) phosphor ceramic
(Elsevier B.V., 2011) Ayvacikli M.; Ege A.; Can N.
Phosphors for radiation detection require efficient energy transfer from the ionization track to the luminescent centers. In this work, the radioluminescence (RL) spectra of SrAl2O4 phosphor ceramics doped with individual trivalent rare earth element (REE) ions (Sm, Eu and Dy) are reported at the room temperature. Although there is some intrinsic UV/blue emission from the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the REE2+ and REE3+ states. The shapes of the emission bands are different for each dopant. The sharp emission properties show that the SrAl2O 4 is a suitable host for rare-earth ion doped phosphor material. © 2011 Elsevier B.V. All rights reserved.
Synthesis and optical properties of Er3 and Eu3 doped SrAl2O4 phosphor ceramic
(2011) Ayvacikli M.; Ege A.; Yerci S.; Can N.
We report, for the first time on luminescence from a Er3 doped SrAl2O4 phosphor. Effects of Eu3 doping were also studied. The influence of rare-earth doping in crystal structure and its optical properties were analysed by means of X-ray diffraction (XRD), Raman scattering, optical absorption, excitation and emission (PL) spectroscopy, thermally stimulated luminescence (TSL) and scanning electron microscope (SEM). Luminescence spectra and luminescence decay curves for Er3 transitions in the near infrared region were recorded. The PL maximum for Eu doped SrAl2O4 is obtained at 620 nm and corresponds to the orange region of the spectrum. Diffraction patterns reveal a dominant phase, characteristic of the monoclinic SrAl2O4 compound and the presence of dopants has no effect on the basic crystal structure of SrAl 2O4. The shapes of the glow curves are different for each dopant irradiated with either a 90Sr90Y beta source, or UV light at 311 nm, and in detail the TL signals differ somewhat between Er and Eu dopants. © 2011 Elsevier B.V. All rights reserved.
Luminescence study of some yttrium tantalate-based phosphors
(2011) Karsu E.C.; Popovici E.J.; Ege A.; Morar M.; Indrea E.; Karali T.; Can N.
Yttrium tantalate (YTaO4), yttrium niobium-tantalate (YTaNbO4), yttrium niobate (YNbO4), europium and terbium activated yttrium tantalate (YTaO4:Eu, YTaO4:Tb) and europium activated yttrium niobate (YNbO4:Eu) phosphors were prepared by solid-state reaction, from a homogeneous mixture consisting of Y 2O3, Eu2O3, Tb4O 7, Ta2O5, Nb2O5 and Na2SO4 as flux. Photoluminescence (PL), thermally stimulated luminescence (TSL), X-ray diffraction (XRD) and scanning electron microscopy (SEM) of yttrium tantalate based phosphors are reported. In the present study TSL characteristics of these phosphors were first investigated and reported after exposure to beta, UV (311 nm) and X-ray radiations. © 2010 Elsevier B.V. All rights reserved.
Photoluminescence investigations of Li 2SiO 3:Ln (Ln=Er 3+, Eu 3+, Dy 3+, Sm 3+) phosphors
(2012) Sabikoglu I.; Ayvackl M.; Bergeron A.; Ege A.; Can N.
In this study, we report a comprehensive structural and photoluminescence (PL) study on lithium metasilicate (Li 2SiO 3) phosphor ceramics doped with four rare earth (RE) ions. X-ray diffraction (XRD) patterns show a dominant phase, characteristic of the orthorhombic structure Li 2SiO 3 compound and the presence of dopants has no effect on the basic crystal structure of the material. The first excited state Er 3+ luminescence at 1.54 μm arises from a sharp atomic-like radiative transition between the 4I 13/2 state and the 4I 15/2 state (ground level) under a 532 nm line of an Ar ion laser excitation. Sm doped samples showed Sm 3+ emission characteristics corresponding to the some 4G 5/2→ 6H j (j=5/2,9/2,11/2) transitions indicating a strong crystal-field effect. PL spectra of Eu doped material exhibited peaks corresponding to the 5D 0→ 7F j (j=0,1,2,3 and 4) transitions under 405 nm excitation. The dominant red color emission at 612 nm from the hypersensitive ( 5D 0→ 7F 2) transition of Eu 3+ indicates the inversion antisymmetry crystal field around Eu 3+ ion, which is favorable to improve the red color purity. Dy doped samples showed the Dy 3+ emission characteristic due to the 4F 9/2→ 6H 13/2 transition. Their relative intensity ratios also suggested the presence of a symmetric environment around the metal ion. We suggest that lithium metasilicate has enough potential candidates to be a phosphor material. © 2012 Elsevier B.V.
Absorption and photoluminescence spectroscopy of Er 3+-doped SrAl 2O 4 ceramic phosphors
(2012) Ayvackl M.; Khatab A.; Ege A.; Şabikoǧlu I.; Henini M.; Can N.
A spectroscopic characterization of Er 3+-doped SrAl 2O 4 phosphor materials synthesized by a solid-state reaction method with Er concentrations varying from 0.1 to 1 mol% has been performed by studying photoluminescence (PL) in the temperature range 10 to 360K and absorption spectra. PL signals containing five emission bands at 1492, 1529, 1541, 1558, and 1600nm, respectively, have been observed at room temperature for Er 3+ transitions in the near infrared region. The samples exhibit a main luminescence peak at 1.54 μm, which is assigned to recombination via an intra-4f Er 3+ transition. Sharp bands centered at around 378, 488, 521, 651, 980, 1492, and 1538nm in the absorption spectra can be associated with transitions from 4I 15/2 level to 2H 9/2, 4F 7/2, 2H 11/2, 4F 9/2, 4I 11/2, 2H 11/2, and 4I 13/2 levels, respectively. The sharp emission peaks and excellent luminescence properties show that SrAl 2O 4 is a suitable host for rare-earth-doped phosphors, which may be suitable for optical applications. © 2012 Taylor & Francis.
Luminescence characterization of cerium doped yttrium gadolinium aluminate phosphors
(Elsevier B.V., 2012) Uysal Satilmis S.; Ege A.; Ayvacikli M.; Khatab A.; Ekdal E.; Popovici E.J.; Henini M.; Can N.
Yttrium gadolinium aluminate ((Y1-xGdx) 3Al5O12:Ce) doped cerium phosphors with the different yttrium and gadolinium concentration were prepared by a wet-chemical route via the reagent simultaneous addition technique (WCS-SimAdd). The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL), radioluminescence (RL) of cerium doped yttrium gadolinium aluminate phosphors. With increasing Gd dopant concentration, the PL intensity was shifted to the red region. Preliminary RL measurements were performed to further evaluate these newly prepared materials. Intense RL was observed that is typical of Ce3+ doped structure. © 2012 Elsevier B.V. All rights reserved.
Radioluminescence study of rare earth doped some yttrium based phosphors
(Elsevier B.V., 2012) Ayvacikli M.; Ege A.; Ekdal E.; Popovici E.-J.; Can N.
This paper reports the luminescence emission spectra of Y(Ta,Nb)O 4 activated by rare earth ions such as Eu3+ and Tb 3+. The influence of these rare earth ions on the radioluminescence (RL) of yttrium niobate and tantalate phosphors was investigated. The luminescent properties were studied under X-ray and preliminary RL measurements to further evaluate prepared materials. The emission centers of the rare earth activators (Eu3+, Tb3+) were found to contribute efficiently to the total luminescence. With their various luminescence chromaticities, these rare earth activated phosphors are promising materials for solid-state lighting applications as well as for X-ray intensifying screens in medical diagnosis, providing the broad band variation of visible RL from blue to red. © 2012 Elsevier B.V. All rights reserved.
Luminescence dating studies of Yeşilova Hoyuk
(Walter de Gruyter GmbH, 2012) Ekdal E.; Ege A.; Karali T.; Derin Z.
Ceramic findings collected from Yeşilova Hoyuk located in Izmir were dated using the thermoluminescence dating technique. The area is of significant archaeological importance since it is the first prehistoric settlement in Izmir. Recent archeological observations suggest that human occupation of the region took place about 8500 years ago comparing to previously determined dates of 5000 years. Three samples collected from the same archaeological layer (Neolithic period) in Yeşilova Hoyuk were dated using the thermoluminescence method. Archaeological doses (AD) were obtained by single aliquot regenerative dose method (SAR) for thermoluminescence (TL) using coarse grain quartz minerals extracted from samples. Thick and thin Al2O3:C thermoluminescence dosimeters (TLD) were used to determine the annual dose rate. The archaeological doses were found to vary from 25.91±0.78 to 26.82±0.68 Gy, and the annual doses were found to be between 3.34±0.24 and 3.47±0.24 mGy/a. The ages obtained for the samples were determined to be 6000±830 BC, 5740±670 BC and 5460±740 years for samples ND1, ND2 and ND3, respectively, which supports the prediction of archeologist that the sampling layer dates from the Neolithic period. © 2012 Silesian University of Technology, Gliwice, Poland 2012.
Spectral emission of rare earth (Tb, Eu, Dy) doped Y2Sn 2O7 phosphors
(2013) Ege A.; Ayvacikli M.; Dinçer O.; Satilmiş S.U.
Radioluminescence (RL) characterization of the yttrium stannate (Y 2Sn2O7) phosphors doped with 1 mol% Tb, Eu and Dy was carried out and significant electronic transitions corresponding to doped rare earth ions were observed. It was seen that all parts of these rare earth ions are included in the phosphor material in their trivalent state. The RL measurement indicates that the series of the emission-state 5D 4→7F6, 5D4→ 7F4, 5D4→7F 3, corresponding to the characteristic 4f→4f intra-configuration forbidden transitions of Tb3+are appeared and that main emission peak occurs at about 542 nm. There are in fact multiple emission lines at each of these due to the crystal field splitting of the ground state of the emitting ions. Eu-doped Y2Sn2O7 sample displayed intense and predominant emission peaks located at 580-650 nm corresponding to the 5D0→7Fj (j=l, 2, 3 and 4) transitions. Red emission coming from the hypersensitive Dy doped phosphor presented luminescence emissions with dominating transitions at 4F9/2→6Hj (j=9/2, 11/2, 13/2 and 15/2). The sharp emission properties show that the Y2Sn 2O7 is a suitable host for rare-earth ion doped phosphor material. © 2013 Elsevier B.V.
Synthesis and luminescence of Tb3+ doped lithium borate (LiBO2)
(2013) Dinçer O.; Ege A.
We report that terbium doped lithium borate phosphors were synthesized by conventional solid state reaction method for the first time. X-ray diffraction (XRD) analysis, radioluminescence (RL) and thermally stimulated luminescence (TSL) were used to investigate structural and luminescence properties of terbium doped lithium borate phosphors. XRD patterns confirm that the lithium borate phosphors sintered at 1200 °C exhibit monoclinic structure. RL spectrum revealed that terbium ions are present in trivalent oxidation states. RL measurements shows that the series of emission state 5D 4→7F6, 5D4→ 7F5, 5D4→7F 4 and 5D4→7F3, corresponding to the typical 4f→4f infra-configuration forbidden transitions of Tb3+, are appeared and major emission peak is around at 541 nm. The TSL kinetic parameters of a newly prepared terbium doped lithium borate phosphor have been calculated. The LiBO2:Tb3+ exhibits two TSL glow curves at around 90 and 155 °C. The kinetic parameters, namely activation energy (trap depth) and frequency factor (s) associated with the main glow peak (155 °C) of the material were determined using peak shape (PS) and various heating rates (VHR) methods. © 2013 Elsevier B.V.
Microstructural and Radioluminescence Characteristics of Nd3+ Doped Columbite-Type SrNb2O6 Phosphor
(Springer New York LLC, 2017) Ekmekçi M.K.; İlhan M.; Ege A.; Ayvacıklı M.
Undoped and different concentration Nd3+ doped SrNb2O6 powders with columbite structure were synthesized by molten salt process using a mixture of strontium nitrate and niobium (V) oxide and NaCl-KCl salt mixture as a flux under relatively low calcining temperature. X-ray diffraction analysis results indicated that SrNb2O6 phases found to be orthorhombic columbite single phase for undoped, 0.5 and 3 mol% Nd3+ doping concentrations. Phase composition of the powders was examined by SEM-EDS analyses. Radioluminescence properties of Nd3+ doped samples from UV to near-IR spectral region were studied. The emissions increased with the doping concentration of up to 3 mol%, and then decreased due to concentration quenching effect. There is a sharp emission peak around 880 nm associated with 4F5/2 → 4I9/2 transition in the Nd3+ ion between 300 and 1100 nm. The broad emission band intensity was observed from 400 to 650 nm where the peak intensities increased by increasing Nd3+ doping concentration. All the measurements were taken under the room temperature. © 2017, Springer Science+Business Media New York.
Thermoluminescence kinetic parameters of yttrium niobate
(Elsevier GmbH, 2022) Ege A.; Özkan A.
Yttrium niobate (YNbO4) phosphorus produced using the solid-state technique by sintering at 1200 °C investigated for thermoluminescence (TL) kinetics after irradiated with ultraviolet radiation (UV). The TL glow curve of UV irradiated yttrium niobate phosphorus recorded with a heating rate of 2 Ks−1 exhibited glow peaks at 366 and 424 K. The TL kinetic parameters belonging to main glow peak (424 K) of yttrium niobate phosphor, namely trap energy (E), frequency factor (s) and kinetic order (b) were investigated using Various Heating Rates (VHR), Computerized Glow Curve Deconvolution (CGCD), and Chen's Peak Shape (PS) methods after exposure to UV radiation. Trap energies of the phosphor by all methods were calculated as 1.09 eV. The frequency factors of the phosphor by CGCD, VHR and Chen's PS methods were obtained as 0.96 × 1012 s−1, 1.38 × 1012 s−1 and 0.98 × 1012 s−1, respectively. The results attained by all methods are discussed and compared. © 2022 Elsevier GmbH
Thermoluminescence Characterization of Rare Earth-Doped Yttrium Stannate Phosphors Deposited by Friction Stir Processing
(Springer, 2022) Durukan Gültepe M.; Ege A.; Küçükömeroğlu T.
The goal of this study is to examine the thermoluminescence (TL) properties of materials obtained by depositing rare earth ion-doped yttrium stannate (Y2Sn2O7) phosphor powders on metallic surfaces using friction stir technique. Y2Sn2O7 phosphors doped with Tb, Eu and Dy rare earth ions were produced by the solid-state reaction synthesis method by sintering at 1450 °C. TL properties of Y2Sn2O7:Eu, Dy and Tb were examined under X-ray irradiation, UV radiation (254 nm) and beta radiation. Thermoluminescence dosimeter (TLD) reader was used for recording the TL glow curves, and linear heating rate was selected as 2 Ks−1. The thermoluminescence glow curves of deposited phosphors showed prominent glow peaks at 225 °C for Y2Sn2O7:Tb, 185 °C and 295 °C for Y2Sn2O7:Eu and 150 and 260 °C for Y2Sn2O7:Dy after irradiated with X-ray radiation. TL properties of phosphor composites deposited by friction stir processing are a pioneering study. © 2021, The Indian Institute of Metals - IIM.

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