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    Relationship Between Growth Speed and Magnetic Properties in Bi-2212/Ag Textured Composites
    (Springer, 2013) Ozkurt, Berdan; Madre, M. A.; Sotelo, A.; Yakinci, M. Eyyuphan; Ozcelik, Bekir; Diez, J. C.
    In this paper, the measured magnetic properties of Bi2Sr2CaCu2O (x) /3 wt.% Ag textured composite materials prepared by a LFZ melting technique at different growth speeds (5, 15, 30, and 60 mm/h) are presented. X-ray diffraction patterns have shown that Bi-2212 phase is the major one in all cases. The magnetization measurements have been carried out as a function of the magnetic field up to 10 kOe. J (c) values, calculated using Bean's model, indicate that the growth speeds have a significant effect on J (c) . It has been found that the maximum critical current density, 4.42x10(5) A/cm(2) at 10 K, has been obtained for the 15 mm/h grown sample.
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    Relationship Between Growth Speed, Microstructure, Mechanical and Electrical Properties in Bi-2212/Ag Textured Composites
    (Springer, 2012) Ozkurt, Berdan; Madre, M. A.; Sotelo, A.; Yakinci, M. Eyyuphan; Ozcelik, Bekir
    Transport properties on Bi-2212 superconductors can be improved by grain orientation methods while mechanical ones can be tuned up by the addition of metallic silver. Both processes can be performed simultaneously using the Laser Floating Zone (LFZ) method. In this work, Bi2Sr2CaCu2O (x) /3 wt.%Ag textured composite materials were prepared by a LFZ melting technique at different growth speeds (5, 15, 30, and 60 mm/h). In all cases, the observed microstructure after annealing shows the Bi-2212 phase as the major one. Although growth speed has no effect on the measured T (c) values, a drastic change on the J (c) values has been found. The best results, both mechanical and transport properties, have been obtained for samples grown at 15 mm/h.
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    Thermoelectric power and thermal conduction studies on the Nd substituted BPSCCO (2234) superconductors
    (Elsevier, 2007) Ozkurt, Berdan; Ocelik, Bekir; Kiymac, Kerim; Aksan, M. Ali; Yakinci, M. Eyyuephan
    In this study, we have carried out thermoelectric power (S-T) and thermal conductivity (kappa-T) measurements from room temperature down to 15 K on Bi1.7Pb0.3-xNdxSr2Ca3Cu4O12+y samples, where 0.0 <= x <= 0.1. The thermoelectric powers, S(T), of the samples have both negative (at high T) and positive values (at low T), and are found to increase with decreasing temperature, reaching maxima (peaks) around their T, values and to drop rapidly to zero below T,. The magnitude of the peaks decreases with increasing Nd-content. The results obtained have been analyzed in terms of the two-band model with linear T-term and Xin's two-band model. A very good agreement between the first model and our thermoelectric power data is obtained, but the fit to the second model is poor. The fittings to the models indicate that while the electrons are effective at higher temperatures, the holes become dominant at lower temperatures, the number of holes and the Fermi energies decrease with increasing Nd-content. Nd substitution also has a considerable effect on the thermal conductivity, kappa. A broad maximum is obtained on kappa versus T plot, just below the T, value of each sample. However, the peaks decrease in intensity and also broaden with increasing Nd concentration. This behavior is believed to be due to the scattering of the carriers. (c) 2007 Elsevier B.V. All rights reserved.