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  • Öğe
    Ultrasonically sprayed cobalt oxide thin films: Enhancing of some physical properties by nickel doping
    (Elsevier B.V., 2021) Kus, Esra; Kucukarslan, Ayse; Demirselcuk, Barbaros; Sarıca, Emrah; Akyuz, Idris; Bilgin, Vildan
    In this study, the effect of Ni doping (3, 6, 9 at%) on structural, optical, electrical and magnetic properties of Co3O4 films was reported. Films were grown at 300 ± 5 °C substrate temperature via ultrasonic spray pyrolysis (USP) technique. The structural analyses showed that undoped and Ni (3%) doped films exhibit an amorphous structure. Ni doping at higher ratios caused the films to have improved crystallinity. Optical band gap values the films were found to be between 2.03 and 2.08 eV with an additional sub-band corresponding to energies varying between 1.35 and 1.46 eV. The electrical conductivity values of the films increased significantly depending on the Ni doping. The hysteresis curves of the films showed that the films have weak ferromagnetic properties. Ni doping significantly improved the structural and electrical properties of Co3O4 films making them suitable materials for technological applications.
  • Öğe
    The role of Eu3+ ion on luminescence, TL kinetic parameters and electrochemical behaviors of Sr0,5Ca0,5WO4 phosphor synthesized via sol-gel technique
    (TUBITAK, 2021) Kati, Mehmet İsmail; Keskin, İlker Çetin; Türemiş, Murat
    The Eu3+doped Sr0,5Ca0,5WO4 has been synthesized by the sol-gel method for the first time. The phosphors were analyzed by XRD, SEM, DTA/TG optical absorption spectra, radioluminescence (RL), photoluminescence (PL), and thermoluminescence (TL) spectra. The energy transfer mechanism was determined on Eu3+ doped Sr0,5Ca0,5WO4 phosphor. The XRD results reveal that the samples exhibit a tetragonal scheelite structure. FT-IR spectra provide the proof of scheelite structure with W-O anti-symmetric stretching vibration in [WO4]2- tetrahedrons at 750-910 cm-1. The Sr0,5Ca0,5WO4 phosphor showed a broad emission between 350-750 nm with a maximum of 506 nm. Sr0,5Ca0,5WO4:0.5Eu3+ phosphor exhibit characteristic emissions of Eu+3 (545, 592, 614, 650, and 700 nm) in the RL spectrum. The host material has excellent energy transfer efficiency for lanthanide ions. The kinetic parameters were calculated by the computerized glow curve deconvolution (CGCD) analysis method. As a result of CGCD, three peaks (Etrap:0.74-1.46 eV) for un-doped Sr0,5Ca0,5WO4 and five peaks (Etrap:0.75-1.28 eV) for Sr0,5Ca0,5WO4: Eu3+ were determined under main TL glow curve. In the cyclic voltammogram of the doped sample, an oxidation peak of about-0.4 eV, which is thought to be derived from Eu3+, was observed. Based on the results, the Sr0,5Ca0,5WO4:Eu+3 phosphors may be potential applicants for LEDs.
  • Öğe
    Sol-gel derived ZnO:Sn thin films and fabrication of n-ZnO:Sn/p-Si heterostructure
    (Elsevier B.V., 2021) Sarıca, Emrah; Gunes, Ibrahim; Akyuz, Idris; Bilgin, Vildan; Erturk, Kadir
    In this work ZnO:Sn thin films were deposited onto glass and p-Si substrates by spin coating of prepared sols which contains different amounts of Zn(CH3COO)2·2H2O and SnCl2 (0, 5, 10 and 15%). Physical properties of ZnO films were examined as a function of SnCl2 in prepared sols. In addition to that, heterostructure examinations were also carried out by depositing all films on p-Si substrates as well. XRD studies revealed that all films have c-axis orientation with crystallite sizes between 38 and 47 nm. AFM and SEM images showed that morphology of the films remarkably deteriorated with the increase in amount of SnCl2 in sol. Optical transmittance and absorbance spectra showed that films have high transmittance and low absorbance in the visible region. Besides, optical band gap increased from 3.27 eV to 3.37 eV. Additional band gap energies were determined for 10% and 15% Sn doped ZnO films. Room temperature photoluminescence spectra for all films were deconvoluted for the evaluation of all emission bands and it was noted that incorporation of SnCl2 into sol led to enhancement of UV-blue emission bands and caused emission bands related to oxygen vacancies to diminish. Four-point-probe measurements revealed that electrical resistivity of ZnO:Sn films increased from 3.20 × 100 Ωcm to 2.82 × 104 Ωcm and diode ideality factor of Ag/ZnO:Sn/p-Si/Au heterostructure was calculated to be in the range of 2.14–4.59 while zero-bias barrier height is in the range of 0.63–0.78 eV.
  • Öğe
    Investigation of spray pyrolyzed cubic structured Cu doped SnS films
    (Taylor and Francis Ltd., 2021) Sarıca, Emrah
    Undoped and Cu doped SnS films were deposited onto glass substrates by spray pyrolysis technique in order to investigate the effect of Cu doping on their physical properties. Surface investigations showed that Cu doping reduced the surface roughness of SnS films from 36.5 to 8.8 nm. XRD studies revealed that all films have recently solved large cubic phase of SnS (π-SnS) with a-lattice of 11.53 Å and Cu doping led to a reduction in crystallite size from 229 to 198 Å. Additionally, all deposited films were found to be under compressive strain. Optical band gaps of SnS:Cu varied in the range of 1.83–1.90 eV. Hall-effect measurements exhibited that all films have p-type conductivity with low hole concentration (∼1011–1012 cm−3) and high electrical resistivity (∼104–105 Ωcm).
  • Öğe
    Improvement of structural, optical and magnetic properties of cobalt oxide thin films by doping with iron
    (Springer Science and Business Media Deutschland GmbH, 2021) Kucukarslan A.; Kus E.; Sarıca, Emrah
    In this study, using the ultrasonic spray pyrolysis technique, undoped and Fe-doped (at 2, 4, 6%) Co3O4 films were deposited on microscope glass substrates at 300 ± 5 °C, and the effect of Fe doping on some physical properties of Co3O4 films was examined. The structural, optical, magnetic and morphological properties of all films were analyzed using X-ray diffractometer, UV–Vis spectrophotometer, vibrating sample magnetometer and atomic force microscope, respectively. Band gap values of Co3O4:Fe films were found to be between 1.98 and 2.12 eV with an additional sub-band corresponding to energies varying between 1.48 and 1.50 eV for all samples. Structural analysis showed that crystallization levels of the films were improved with the Fe doping. Also, hysteresis curves of the films showed weak ferromagnetic characteristics and the magnetic behavior of the films was found to be sensitive to doping amount of Fe. It was found that Fe doping has beneficial effect on some physical properties of Co3O4 films.
  • Öğe
    Comprehensive study on structural, thermal, morphological and luminescence (RL, PL, TL) properties of CaLa2(WO4)4: Tb3+, Dy3+ phosphors synthesized via sol-gel method
    (Elsevier Ltd, 2021) Türemiş, Murat; Keskin İ.Ç.; Katı M.İ.; Çetin A.; Ay K.; Kibar R.
    Tb3+/Dy3+ co-doped CaLa2(WO4)4 (CLW: Tb3+/Dy3+) and its derivatives were synthesized by the sol-gel method. The morphology, thermal, structure and luminescent-optical properties the as-prepared light-emitting phosphors were characterized by utilizing scanning electron microscopy (SEM), differential thermal analysis (DTA)-thermogravimetric analysis (TG), X-ray diffraction (XRD) and radioluminescence (RL or X-ray luminescence) - photoluminescence (PL) –thermoluminescence (TL or TSL) - optical absorption spectrometry. The Tb3+ and Dy3+ ions were singly or doubly doped and the results were examined in detail. Moreover, for these phosphors, the energy transfer mechanisms which depend on RL and PL spectra were determined. The samples excited by X-ray demonstrate characteristic luminescence peaks of Dy3+ (422, 480, 575, 663 and 747 nm) and Tb3+ (489, 544, 586, 620, 652 and 675 nm). These emissions are similar for RL and PL measurements. It could be said that the energy transfer efficiency of the host material is perfect for rare-earth ions. The synthesized phosphors exhibit various colors from yellow to blue under UV excitation. The optical band gaps of host CLW, CLW: Tb3+, CLW: Dy3+ and co-doped CLW: Tb3+/Dy3+ were calculated at values 3.83 eV, 3.44 eV, 3.64 eV and 3.52 eV, respectively. From the results obtained, the CaLa2(WO4)4: Tb3+, Dy3+phosphors may be one of the potential candidates for light-emitting diode.
  • Öğe
    Investigation on Cathodoluminescence Properties of Copper Implanted ZnO Samples
    (2019) Arslanlar, Yasemin Tuncer; Keskin, İlker Çetin; Katı, Mehmet İsmail; Türemiş, Murat; Çetin, Ahmet; Kibar, Rana
    ZnO single crystals has been implanted with 400 keV Cu ions at fluences of 2,5 x 1016 ions/cm2 at room temperature. The cathodoluminescence (CL) measurements of pure and Cu implanted samples has been reported at UV-visible range at both room and different temperatures. After the implantation process, the samples were annealed for 1 hour at 1000ºC. The effects of ion implantation and annealing temperature and on the CL signals were researched with the data obtained. The CL spectrum of pure ZnO exhibited two emission bands at 385 nm and 550 nm. There are some changes in the emission bands in the CL spectrum that are thought to be due to the presence of Cu ions. Also it is possible to say that the annealing temperature can strongly influence CL intensity.
  • Öğe
    Charged Particle Interactions of Human Organs and Tissues in Heavy Ion Therapy; Effective Atomic Number and Electron Density
    (2020) Büyükyıldız, Mehmet
    In this work, various organs of human and tissues were studied in terms of the effective atomic numbers (Zeff) and electron densities (Ne) in the continuous kinetic energy region for different types of heavy ions. Variations of Zeff and Ne with kinetic energy were investigated and significant variations were noted. In addition, water and tissue equivalences of the given materials with respect to their Zeff and Ne were evaluated based on the results obtained. The best water equivalents were found to be Urinary Bladder_Urine for H, He and C ions and Skeleton Cartilage for Ne ion since differences in Zeff relative to water for H (?%3), He (?%1), C (?%1) and Ne (?%6) ions were significantly low. Moreover, variations in water equivalences of the materials have been discussed in detail in the continuous energy region. The reported data should be useful when heavy ions are intended to be used in these materials for radiotherapy and dosimetry applications as they represent the interaction of ions with these materials in the continuous kinetic energy region.
  • Öğe
    Effects of the oxide/interface traps on the electrical characteristics in Al/Yb2O3/SiO2/n-Si/Al MOS capacitors
    (Springer, 2021) Morkoç, Berk; Kahraman, A.; Yılmaz, E.
    In the present work, we examine the effect of structural modifications occurring during the fabrication of Al/Yb2O3/SiO2/n-Si/Al MOS capacitors under different annealing temperatures on the electrical characteristics of the capacitors. The structural properties depending on post-deposition annealing (PDA) were evaluated based on the crystal properties, elemental compositions, and bonding structures of Yb2O3/SiO2 films, while the electrical characteristics were determined by capacitance–voltage (C–V) measurements. The smallest particle size was found in the film annealed at the highest PDA temperature. In all films, the Yb atom concentration was determined higher than the others. The non-stoichiometric silicate (YbSixOy) layer was detected in film structure annealed at 400 °C. The Yb 4d and O 1s spectra shifted toward higher binding energies with increasing depth in the films. The density of bonded oxygen species decreased with increasing PDA temperature. It was obtained that capacitance in accumulation region (Cacc), dielectric constant (?k), and series resistance (Rs) values tend to decrease with both increasing frequency and PDA temperature. The highest and lowest interface state density (Nit) was found for capacitors obtained from as-deposited and annealed at 400 °C structures, respectively. The effective oxide charge density (Qeff), which expresses the net charge trapped in the oxide layer, is at the 1011 level. The barrier heights (?B), which generally tend to increase, have shown that acceptor-type interface states are active on electrical characteristics. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
  • Öğe
    Study of the hydrothermal crystallization process of barium titanate by means of X-ray mass attenuation coefficient measurements at an energy of 59.54 keV
    (Elsevier Science Inc, 2017) Akbulut Özen, Songül; Ozen, Murat; Sahin, Mehmet; Mertens, Myrjam
    In this work, the X-ray mass attenuation coefficients of hydrothermally synthesized barium titanate (BaTiO3) samples were calculated with the purpose of determining the crystallization sequence of BaTiO3. Hydrothermally synthesized samples prepared at 100 degrees C and 200 degrees C, and reacted for varying reaction times between 15 min up to 120 h were studied. Attenuation coefficient measurements were done with a coaxial HPGe gamma detector (Ortec, GEM55P4-95) with a working range in the X-ray energy region. The samples were made into pellets and were exposed to Am-241 radioisotopes at an energy of 59.54 keV for 300 s. Additionally, FT-Raman and XRD measurements were done to support the X-ray mass attenuation measurements. It was found that secondary barium titanate (BT) phases (BaTi2O5 and Ba2TiO4) were formed from the precursor material at the early stages of the hydrothermal reaction and that phase pure BaTiO3 was formed at longer reaction times. The sequence of barium titanate crystallization was determined as follows: BaTi2O5; BaTi2O5 and BaTiO3; BaTi2O5, Ba2TiO4 and BaTiO3: and phase pure BaTiO3.
  • Öğe
    Investigation of heavy metal distributions along 15m soil profiles using EDXRF, XRD, SEM-EDX, and ICP-MS techniques
    (Wiley, 2018) Akbulut Özen, Songül; Ozkalayci, Fatih; Cevik, Ugur; Van Grieken, Rene
    The research of soil contamination by heavy metal is an important field due to its environmental and health implications. The goal was to study the elemental mobility as a function of depth. For this reason, the distribution of heavy metals (V, Cr, Co, Ni, Cu, Zn, As, Sn, and Pb) was investigated along soil profiles up to a depth of 15m at 9 sampling sites in the Nilufer industrial district (Bursa, Turkey). Elemental analyses were done with the Epsilon 5 energy dispersive X-ray fluorescence and inductively coupled plasma mass spectrometry equipment. Particle analysis was performed with a JEOL scanning electron microscope equipped with a Si(Li) X-ray detector. The crystallographic compositions of oxide compounds in soil samples were identified by a Rigaku X-ray diffraction instrument. Different parameters such as the soil's chemical (mineralogical structure, pH, and electrical conductivity) and physical properties (the number of blows, the stiffness index, the liquidity index, the plasticity index, and the water content) were analyzed. To assess the mobility of the heavy metals, diffusion (D) and convection coefficients (?) were calculated with the finite difference method. Convection was determined to dominate the studied region. In addition, the mobility coefficient was determined for each metal. High mobilities were determined for Zn and V, moderate mobilities for Cr, Ni, Cu, and As, and low mobilities were determined for Co and Pb. The results revealed that elements had reached depths of up to 15m, causing irreversible soil contamination that may lead to environmental health issues.
  • Öğe
    Indoor and outdoor radon measurements at lung cancer patients' homes in the dwellings of Rize Province in Turkey
    (Springer, 2018) Akbulut Özen, Songül; Celik, Necati; Dursun, Emrehan; Taskin, Halim
    In this study, indoor and outdoor radon (Rn-222) surveys were carried out in the summer and winter seasons in homes of one hundred lung cancer patients in the year 2013-2014. The aim was to investigate the relationship between radon and cancer patients. Lung cancer patients completed a questionnaire concerning their living environment, various physical parameters and living habits. Pearson correlation and t tests revealed no meaningful results between radon concentrations, on one hand, and environmental and personal living habits, on the other hand. Consequently, the BEIR VI model was adapted and Rn-222 exposure was estimated to be responsible for about 12% of the lung cancer incidences in the winter season and around 5% in the summer season in the Rize Province. However, due to the limited number of data and numerous parameters that could lead to lung cancer, the estimations done with the model should be taken very lightly. The annual effective doses due to inhalation of indoor and outdoor Rn-222 were estimated to be, respectively, 1.43 and 0.94 mSv y(-1). The indoor and outdoor annual effective doses were, respectively, close and below the world annual effective dose (1.3 mSv y(-1)). At the district level, the indoor annual effective dose equivalent in the A degrees yidere district was 4.52 mSv y(-1), which was 3.5 times greater than the world average. The number of patients in the majority of the houses in this district was more than one.
  • Öğe
    X-ray irradiated thermo- and radioluminescence, structural and thermal characterization of septarian (powder&bulk) from Madagascar
    (Elsevier, 2018) Keskin, Ilker Cetin; Kati, Mehmet Ismail; Türemiş, Murat; Gultekin, Serdar; Ustun, Siileyman; Cetin, Ahmet
    The luminescence properties of septarian have been investigated for the first time in this study, which has been the subject of many studies in both geological and geophysical fields. This sediment with a calcium carbonate structure exhibited high luminescence properties with X-ray excitation. The radioluminescence (RL) and thermoluminescence (TL) properties were investigated as well as their structural (FT-IR, XRD), morphological (SEM), thermal (TG-DTA) and absorption (UV-Vis-NIR) properties of this sediment. The broad RL peak of septarian was observed at 640 nm. There was a significant increase in the RL intensities of the sifted samples compared with the bulk sample. The TL glow curves of septarian irradiated with X-rays exhibited intense main TL glow peak having the maximum temperatures at 116 degrees C and about 390 degrees C with a heating rate of 2 degrees C/s. Also; the TL kinetic parameters were reported; activation energy (E), frequency factor (s) and the order of kinetics (b) of the first peak have been determined in detail by using peak shape (PS) and Computerized Glow Curve Deconvolution (CGCD) methods. SEM and EDS analysis were performed for the two different layers of septarian. The light colored side with the amorphous structure of the sample has more impurities (such as Fe, Al, Zr, K) than the crystallized and darker side.
  • Öğe
    Optimizing Optical and Structural Properties of Nanocomposites by ZnO and BP-3
    (Maik Nauka/Interperiodica/Springer, 2018) Türemiş, Murat; Keskin, I. C.; Kati, M. I.; Kibar, R.; Sirin, K.; Canli, M.
    This study aims to find out usage of zinc oxide (ZnO) and 2-hydroxy-4-methoxybenzophenone (BP-3) for getting better optical and structural properties of nanocomposites. Polymer nanocomposites were prepared by adding zinc oxide for minimizing UV rays effects of the sun with the particle size of nanometer in different ratios to a low density polyethylene (LDPE). The polymer mixtures were synthesized by mixing nanocomposite samples with BP-3 featuring UV stabilizer. Besides making tensile testing measurements, in order to find out the optical, structural, mechanical and thermal changes, the new polymer nanocomposites were characterized by XRD, TG-DTA spectra, and SEM images. The samples with zinc oxide which show luminescent properties were examined in terms of radioluminescence features. Radioluminescence spectrum showed characteristic peaks of zinc oxide dispersed nanocomposites prepared with LDPE. The intensity of the characteristic peaks at 530 and 390 nm (exciton) increased by increasing rates of nanopowder zinc oxide while adding BP-3 to the composites caused a decrease in intensity of radioluminescence.
  • Öğe
    Iron doped ZnO thin films deposited by ultrasonic spray pyrolysis: structural, morphological, optical, electrical and magnetic investigations
    (Springer, 2018) Bilgin, Vildan; Sarıca, Emrah; Demirselcuk, Barbaros; Turkyilmaz, Seren
    In this work, undoped and Fe-doped ZnO thin films at various concentrations (2, 4 and 6 at.%) were deposited onto glass substrate by using ultrasonic spray pyrolysis in order to investigate the effect of Fe doping on the structural, morphological, optical, electrical and magnetic properties of ZnO thin films. X-ray diffractometer (XRD) results revealed that all deposited thin films have hexagonal wurtzite structure and Fe doping led to decrease in mean crystallite size. Atomic force microscopy images showed that thin films were composed of tightly packed grains. Optical examinations indicated that optical transmittance remarkably decreased with the increase in the amount of Fe concentration in thin films. Additionally, optical band gap of deposited films were determined in the range of 3.26-3.29 eV. It was determined that all deposited thin films have n-type conductivity and electrical resistivity increased up to 253.6 Omega cm as a consequence of Fe doping. Vibrating sample magnetometer measurements showed that all films have ferromagnetic behavior.
  • Öğe
    The effect of energy resolution of detection instrument on mass attenuation coefficient
    (Iop Publishing Ltd, 2018) Celik, N.; Akbulut Özen, Songül; Demirtas, O. F.; Cevik, U.
    The effect of energy resolution of two detection systems, HPGe and NaI(T1), was determined by Monte Carlo (MC) calculation on mass attenuation coefficients of magnesium (Mg) and tungsten (W). In order to reveal the energy resolution effect, the detectors' collimator diameters were changed from 2 mm to 20 mm while sending collimated photon beams to the absorber material. It was observed that mass attenuation coefficients were increased with increasing collimator diameters. The performances of HPGe and NaI(T1) detectors were quantified. The calculated results were compared with experimental results for Mg at energy of gamma rays 662 keV for different collimator diameters using both HPGe and NaI(T1). It was observed that the MC calculation results were in a good agreement with the experimental data within the relative error from around 4% to 8%.
  • Öğe
    Comparison of active and passive radon survey in cave atmosphere, and estimation of the radon exposed dose equivalents and gamma absorbed dose rates
    (Taylor & Francis Ltd, 2019) Akbulut Özen, Songül; Cevik, Ugur; Taskin, Halim
    Radon (Rn-222) measurements were conducted in the Pileki Cave with Radim 3A Active Radon Monitor equipment. Measurements were also done with the passive sampling method with CR-39 nuclear track detectors by exposing them for three months in the cave. Radon concentrations obtained from the active and passive sampling methods showed that, firstly, the concentrations inside the cave measured by the latter method differed greatly due to high humidity levels up to 88%. The total inside radon exposure dose equivalent people were subjected to was estimated to be 19 mu Sv a(-1) for visitors and 24,065 mu Sv a(-1) for guides. The gamma absorbed dose rates were determined for inside and outside the cave. The dose rates were calculated by means of using the Ra-226, Th-232 and K-40 activity concentrations and by means of real-time measurements. The gamma absorbed dose rates were found to be much higher than the value of 55 nGy h(-1) given by UNSCEAR. In addition, the mineralogical compositions and elemental analyses of samples taken from the cave were determined by XRD and WD-XRF methods.
  • Öğe
    Effects of CdS quantum dot in polymer nanocomposites: In terms of luminescence, optic, and thermal results
    (Pergamon-Elsevier Science Ltd, 2019) Keskin, Ilker Cetin; Türemiş, Murat; Kati, Mehmet Ismail; Kibar, Rana; Cetin, Ahmet
    CdS quantum dots (QDs) which have unique luminescence efficiency were synthesized by two-phase method using oleic acid (OA) as a surfactant. The nanocomposites have been obtained by blended CdS quantum dots with low-density polyethylene (LDPE) in different ratios. Primarily, radioluminescence (RL) properties were investigated as well as their structural (FT-IR, XRD), morphological (TEM, SEM), thermal (TG-DTA) and absorption (UV-Vis) properties of these nanocomposites. The RL peaks of OA-capped CdS QD were observed at 456 nm and 655 nm. As a consequence of the nanocomposites being doped with powder CdS QD, a significant blue shift was observed in the absorption bands. The optical band gap of CdS was calculated as- 2.3 eV. The nanocomposites blended with CdS QD, this value increased to- 2.7 eV. It has also been observed that nano particles cause nanocomposites to have lower melting temperatures.
  • Öğe
    Structural, optical, luminescence properties and energy transfer mechanism of Tb3+/Eu(3+)co-doped SrLa2(MoO4)(4) phosphors produced by sol-gel process
    (Elsevier Science Sa, 2019) Keskin, I. C.; Gultekin, S.; Kati, M. I.; Türemiş, Murat; Ay, K.; Arslanlar, Y.
    Tb3+/Eu3+ co-doped SrLa2(MoO4)(4) have been synthesized using the sol-gel process. The as-produced light-emitting phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA)/thermogravimetric analysis (TG), optical absorption spectra, radioluminescence (RL), and photoluminescence (PL) spectra. The effect of Tb(3+)and Eu(3+)doping concentrations on the RL and PL intensity of host material was analyzed in details. Furthermore, the energy transfer mechanism based on RL spectra were determined of Tb3+/Eu(3+)co-doped SrLa2(MoO4)(4) phosphors. When the samples excited by X-ray, the SrLa2(MoO4)(4) phosphors exhibit characteristic emissions of Tb3+ (489, 544, 586, 620 and 675 nm) and Eu(3+)d (545, 592, 614, 650 and 700 nm). Also, similar emissions are observed in the results of PL spectra, when the samples excited by 488 nm. The host material has excellent energy transfer efficiency for lanthanide ions. In addition, the luminescence spectra indicated that the energy transfer is also effective between from Tb3+ to Eu(3+)and vice versa. The CIE parameters are calculated to characterize the color emission. Under UV excitation, the synthesized materials display different color from green to red. Based on the results, the SrLa2(MoO4)(4:Eu)(3+)(3+)(,Tb) phosphors may be potential candidates for light-emitting diode. (C) 2019 Elsevier B.V. All rights reserved.
  • Öğe
    Estimation of radon flux spatial distribution in Rize, Turkey by the artificial neural networks method
    (Pergamon-Elsevier Science Ltd, 2019) Yesilkanat, Cafer Mert; Akbulut Özen, Songül
    In this study, average radon flux distribution in the Rize province (Turkey) was estimated by the artificial neural networks (ANN) method. For this purpose, terrestrial gamma dose rate (TGDR), which is defined as an important proxy in determining radon flux distribution, was used. Input parameters that were used for ANN were the natural radionuclide (U-238, Th-232 and K-40) activity values in soil samples taken from 64 stations in Rize Province, data from ambient gamma dose rates (AGDR) directly affecting the distribution of radon flux and data of geographical coordinates. Randomly chosen 42 stations were used for ANN training and data from 22 stations were used for testing the ANN model. Performance test results gave a Pearson's r value of 0.60 (p < 0.001) and RMSE of 0.296. The area that was used for the model was divided into grids of 100 m by 100 m and a spatial distribution map was composed by using ANN predicted radon flux rates at grid nodes, whereby natural radionuclide values and Ordinary Kriging predicted values of external gamma dose rates were used for composing the map.