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Article Citation - WoS: 11Citation - Scopus: 11Microstructural, thermal, and electrical properties of Bi1.7V0.3Sr2Ca2Ca3Ox glass-ceramic superconductor(Wiley-v C H verlag Gmbh, 2004) Kayed, TS; Calinli, N; Aksu, E; Koralay, H; Günen, A; Ercan, I; Cavdar, SA 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.Article Citation - WoS: 9Citation - Scopus: 9Electrical Properties of Bi1.5znsb1.5< Pyrochlore Ceramics(Wiley-v C H verlag Gmbh, 2003) Kayed, TS; Mergen, ABi1.5ZnSb1.5O7 pyrochlore samples were prepared by solid state reaction method. They were examined by x-ray diffraction and scanning electron microscopy. Single phase, belongs to the cubic pyrochlore structure, with a lattice parameter of 10.442 Angstrom and grain size that varies from 16 to 20 mum was obtained. The electrical properties were measured at different temperatures in the range 15-330 K under different applied magnetic fields up 1.4 T. In our measurements for Hall coefficient, Hall resistivity, and mobility; we noticed an anomalous behavior at two temperatures (around 250 and 310 K) which was supported by the I-V measurements (double transition of the slope of I-V characteristics (beta) at the same temperatures). This was discussed in terms of polarization phenomenon and mixed ionic-electronic conduction. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Article Citation - WoS: 6Citation - Scopus: 8Temperature and Magnetic Field Effects on the Carrier Density and Hall Mobility of Boron-Doped Tl-Ba Superconductor(Elsevier Science Sa, 2005) Kayed, TS; Qasrawi, AFBoron-doped T1-based superconductor was prepared by adding an amount of 1 wt.% B to the Tl1.8Ba2Ca2.2Cu3Ox, compound. The usual solid-state reaction method has been applied under optimum conditions. The X-ray data of the sample show a tetragonal structure with a high ratio of T1-2223 superconducting phase. The sample showed a transition at 125 K and the zero resistance was observed at 120 K. The magnetic field and temperature effects on the normal state electrical resistivity, carrier density, and Hall mobility have been investigated. Both temperature and magnetic field significantly affect the resistivity behavior. The zero field resistivity was found to vary exponentially with temperature with a slope revealing activation energy of 27.5 meV. When the magnetic field is applied, the resistivity varied up-normally in the temperature region of 160-240 K. The temperature dependent carrier concentration calculated from the Hall coefficient data varied linearly with the applied magnetic field. This effect was attributed to the increase in the hole effective mass upon field increment. The temperature-dependent carrier concentration data at several applied fields were analyzed by the single donor-single acceptor model to obtain the values of effective masses. The temperature and magnetic field dependent normal state Hall mobility was found to be limited by the scattering of acoustic phonons. (c) 2005 Elsevier B.V. All rights reserved.
