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    Effects of Nb2O5 addition on superconducting properties of BSCCO
    (PERGAMON-ELSEVIER SCIENCE LTD, 2007) Ghazanfari, Nader; Kilic, Ahmet; Gencer, Ali; Oezkan, Huesnue
    The effects of Nb2O5 addition on (Bi, Pb)(2)Sr2Ca2Cu3O10 superconducting polycrystalline samples prepared by conventional solid state reaction method in bulk forms have been investigated. Samples were prepared and then characterized by X-ray diffraction, SEM microstructural analysis, DC electrical, and AC susceptibility measurements. X-ray diffraction analysis shows that both (Bi, Pb)-2223 and Bi-2212 phases coexist in the studied samples. I-V characterization and AC susceptibility measurements reveal that Nb addition increases critical current density. The enhancement of the J(c) may be caused by improvement of the grain connectivity with Nb additions. (c) 2007 Elsevier Ltd. All rights reserved.
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    Enhancement in the high-T-c phase of BSCCO superconductors by Nb addition
    (IOP PUBLISHING LTD, 2007) Sozeri, Huseyin; Ghazanfari, Nader; Ozkan, Husnu; Kilic, Ahmet
    Pure and Nb2O5 added Bi1.6Pb0.4Nbx Sr2Ca2Cu3O delta superconductors ( x varies up to 0.30) were synthesized by the solid state reaction method. Structural and superconducting properties of the samples were investigated. The fraction of the high-T-c phase ( 2223) increases with Nb addition up to x = 0.10, for which a nearly single 2223 phase was obtained. The critical temperature of the samples increases from 96 to 104 K with doping up to x = 0.20 and a further increase in Nb decreases the Tc sharply. Similarly, there is a considerable enhancement in the critical current density ( jc) of the samples in the same doping range. Both AC susceptibility and transport measurements showed that the optimum Nb concentration is x = 0.20. The out- of- phase component of the AC susceptibility measurements showed that inter- grain coupling was enhanced up to the same doping level. Nb additions above x = 0.30 decrease the fraction of the high- Tc phase and degrade the superconducting properties. Present measurements indicate that x = 0.20 is the optimum Nb concentration in the BSCCO superconductor to enhance phase purity, inter- grain coupling and superconducting parameters ( Tc and j(c)).