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  • Küçük Resim
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    Fundamental and high-order harmonic susceptibilities of a BSCCO(2223) bulk superconductor
    (Elsevier Science Bv, 2003) Aksu, E.; Gencer, A.; Yilmaz, H.; Nezir, S.
    Measurements of fundamental and high-order harmonic susceptibilities, chi(n), = chi(n)' + ichi(n)" (n = 1, 2, 3, 5 and 7), were made on a cylindrical BSCCO(2223) bulk sample in the range 15-120 K at fields ranging from 8 to 1600 A/m and 1000 Hz frequency. They exhibit dependence on the amplitude of the ac field. The observed dependences were analyzed by using the Bean model. We have obtained an empirical function for the penetration field H-p = H-alpha(1 - t)(beta), with t = T/T-cb. Best fitting to data was obtained with parameters H-alpha approximate to 3.3 x 10(4) A/m and beta = 2.05. In addition, ac losses were calculated at some fixed temperatures to compare theoretical expectations. The experimental values agree well with the theoretical findings. AC losses were calculated under external fields ranging from 0 to 1600 A/m and, at 84.35 K, the experimental results are shown to agree well with the theoretical values. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Küçük Resim
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    Microstructural, thermal, and electrical properties of Bi1.7V0.3Sr2Ca2Ca3Ox glass-ceramic superconductor
    (Wiley-V C H Verlag Gmbh, 2004) Kayed, T.S.; Calinli, N.; Aksu, E.; Koralay, H.; Gunen, A.; Ercan, I.; Cavdar, S.
    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.