Yazar "Ercan, İsmail" seçeneğine göre listele

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    The effect of zn substitution of ca in BiPbSrCaCuO superconductors sintered at 830 degrees C
    (Springer, 2009) Kocabaş, Kemal; Şakiroğlu, Serpil; Çiftçioğlu, Muhsin; Ercan, İsmail; Epik, Hakan
    The effect of partial substitution of Ca by Zn in Bi1.7Pb0.3Sr2Ca2-xZnxCu3Oy at x = 0.00, 0.05, 0.10, 0.15 and 0.20 levels on the electrical and structural properties was investigated in this work. The characterization of the ceramics prepared by the conventional solid-state reaction method were done by resistance-temperature measurements, XRD, SEM and density analysis. Low levels of Zn substitution of Ca caused significant changes in the properties of the ceramics. The low-T-c superconducting properties were enhanced and the fraction of the low-T-c (2212) phase were found to increase at x = 0.15 level of Zn substitution at 830 degrees C sintering temperature. Zero resistance was observed only in sample D with x = 0.15 and the T-c was determined as 92 K. The SEM micrographs and the density analysis have shown that this was the densest packed ceramic.
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    Fabrication and some physical properties of AgIn5S8 thin films
    (Elsevier BV, 2004) Qasrawi, A.F.; Kayed, T. S.; Ercan, İsmail
    AgIn5S8 thin films are deposited on glass substrates, kept at 300 K, by thermal evaporation of AgIn5S8 single crystals under the pressure of 10-5 Torr. The X-ray fluorescence analysis revealed that the films have a weight percentage of ?11.5% Ag, 61.17% In, and 27.33% S which corresponds to 1:5:8 stoichiometric composition. X-ray analysis of the films reveals the polycrystalline nature of the films. The lattice parameter (a) of the films was calculated to be 10.784(5) Å. The dark n-type electrical conductivity of the films was measured in the temperature range of 30-350 K. The conductivity data analysis shows that the thermionic emission of the charge carriers having activation energies of 147 and 224 meV in the temperature ranges of 130-230 and 240-350 K, respectively, are the dominant transport mechanism in the films. The variable range hopping transport mechanism is dominant below 130 K. The room temperature photocurrent-photon energy dependency predicts a band gap of 1.91 eV of the films. The illumination intensity-photocurrent dependency measured in the intensity range of 13-235 W cm-2 reveals monomolecular recombination (linear) in the films and bimolecular recombination (sublinear) at the film surface corresponding to low and high applied illumination intensities, respectively. The time-dependant photocurrent measured at fixed illumination intensity reveals a response time of 0.85, 2.66 and 10.0 s in the time periods of 0-0.5, 0.5-1.0, and 1.0-10.0 s, respectively. © 2004 Elsevier B.V. All rights reserved.
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    Gamma irradiation of bulk MgB2 superconductor
    (Springer, 2013) Kayed, Tarek S.; Ercan, İsmail; Alagha, Omar
    Current-voltage (I-V) characteristics of MgB2 bulk sintered superconductor, prepared from the commercially available powder (Alfa-Aesar), have been investigated before and after several gamma irradiations up to 5000 MR. A minor increase in the normal state resistance of the sample was observed up to 5000 MR without any change in its critical temperature (T (c) ). I-V characteristics before and after gamma irradiation with different doses up to 5000 MR were shown and fitted to the expression VaeI (beta(T,B)) where beta approaches unity near T (c) before and after gamma irradiation. A decrease in the critical currents (I (c) ) with gamma irradiation up to 1000 MR was observed; after which they start to increase with higher irradiations up to 5000 MR without exceeding the critical currents before irradiation.
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    Magnetic properties of trinuclear Ni-M-Ni complexes, M = Mn, Co and Ni
    (Elsevier, 2006) Atakol, Orhan; Boca, Roman; Ercan, İsmail; Ercan, Filiz; Fuess, Hartmut; Haase, Wolfgang; Herchel, Radovan
    A tetradentate ligand, abbr. L2- =dmSALPD(2-) = N,N'-bis(sahcylidene)-1,3-propanediaminato dianion, has been complexed with metal ions in the presence of dimethylformamide (dmf) and nitrite anion. As a result, trinuclear molecular complexes of the type [M-II- {Ni(NO2(L2-)(dmf)}(2)], where M-II = Mn(II), Co(II) and Ni(II) were obtained. The magnetic susceptibility and magnetization data were treated simultaneously during the fitting procedure. In addition to the isotropic exchange, the zero-field splitting parameters D-A were added to the spin Hamiltonian. An anti-ferromagnetic interaction was found in all complexes and the single ion magnetic anisotropy parameter for the Ni(II) peripheral centers adopt considerable values.
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    Microstructural, thermal, and electrical properties of Bi1.7V0.3Sr2Ca2Ca3Ox glass-ceramic superconductor
    (Wiley-V C H Verlag Gmbh, 2004) Kayed, Tarek Said; Çalınlı, N.; Aksu, Erhan; Koralay, Haluk; Günen, A.; Ercan, İsmail; Aktürk, Selçuk; Çavdar, Şükrü
    A glass-ceramic Bi1.7V0.3Sr2Ca2Cu3Ox superconductor was prepared by the melt-quenching method. The compound was characterized by scanning electron microscopy, x-ray diffraction, differential thermal analysis, current-voltage characteristics, transport resistance measurements, and Hall effect measurements. Two main phases (BSCCO 2212 and 2223) were observed in the x-ray data and the values of the lattice parameters quite agree with the known values for 2212 and 2223 phases. The glass transition temperature was found to be 426 degreesC while the activation energy for crystallization of glass has been found to be E-a = 370.5 kJ / mol. This result indicates that the substitution of vanadium increased the activation energy for the BSCCO system. An offset T-c of 80 K was measured and the onset T-c was 100 K. The Hall resistivity rho(H) was found to be almost field-independent at the normal state. A negative Hall coefficient was observed and no sign reversal of rho(H) or RH could be noticed. The mobility and carrier density at different temperatures in the range 140-300 K under different applied magnetic fields up to 1.4 T were also measured and the results are discussed.
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    Structural analysis of bis{(N,N -dimethylformamide) (mu-formato)[mu-bis(salicylidene)-1,3-propanediaminato] nickel(II)}copper(II) and zinc(II) monohydrate hetero-trinuclear complexes
    (Wiley-V C H Verlag Gmbh, 2004) Ercan, Filiz; Ateş, Meltem B.; Ercan, İsmail; Durmuş, Sefa; Atakol, Orhan
    The two linear hetero-trinuclear metallic complexes with Cu2+, Ni2+ and Zn2+ ions, [CuNi2 {(CHO2)(SALPD)[(CH3)(2)NCHO]}(2)],(I) and [ZnNi2{(CHO2)(SALPD)[(CH3)(2)NCHO]}(2)],(II), form crystals which belong to the monoclinic system, space group P2(1)/c, with unit cell dimensions a = 10.537(4), b = 16.612(5), c = 13.837(3) Angstrom, beta = 111.09(5)degrees, V = 2259.8(12) Angstrom(3) in (II) and a = 10.525(4), b = 16.658(5), c = 13.826(3)Angstrom, beta = 111.11(5)degrees,V = 2261.4(8) Angstrom(3) in (II), respectively. The coordinations around the M (Ni2+, Cu2+, Zn2+) ions in the title complexes are distorted octahedrals. The stereochemistries of the bridge ligands, linking to the metal ions each other, are changed between Ni...M (Cu2+, Zn2+) distances. The Ni...M (Cu2+, Zn2+) distances are 3.0469(13) and 3.0645(14), respectively. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Synthesis, crystal structure and magnetic behaviour of a mononuclear Fe(III) - schiff base metal complex
    (Oldenbourg Verlag, 2006) Nazır, Hasan; Akben, Nimet Sapmaz; Ateş, Meltem Bürke; Sözeri, Hüseyin; Ercan, İsmail; Atakol, Orhan; Ercan, Filiz
    A complex from Fe(II) and a hexa-dentate linear ligand containing O2N4 donor atoms were prepared and the structure enlightened with X-ray diffraction. The Fe(II) ion in the complex was seen to be oxidized to form a Fe(III) complex, [C20H24Cl3N4O2]Fe and the three chloride ions were situated at a distance of Fe...Cl(1) 3.976(5), Fe... Cl(2) 4.479(3) and Fe... Cl(3) 7.509(4) (A) over circle outside the coordination sphere. The Fe(III) ion has an octahedral coordination sphere and as expected the two oxygen donor atoms are coordinated in a -cis position. The Fe-O, Fe-N-imin and Fe-N-amine distances are 1.880(3) (A) over circle, 1.931(4) (A) over circle and 2.004(4) (A) over circle, respectively.