Akademik Veri Yönetim Sistemi
Journal of Materials Science: Materials in Electronics, cilt.25, sa.6, ss.2456-2462, 2014 (SCI-Expanded)
In the present work, the effect of co-doping of Ta and Nb with nominal composition of (BiPb) 2 Ta x Sr 2 Ca 3 Cu 4-y Nb y O 12+δ where x = 0.1 and y = 0.0, 0.025, 0.05, 0.075, and 0.1 were investigated. The samples were prepared by using the well-known conventional standard solid-state reaction method. The magnetoresistance measurements were studied for different values of the applied magnetic field. The activation energies, irreversibility fields (H irr ), upper critical fields (H c2 ) and coherence lengths at 0 K (ζ(0)) were calculated from the resistivity versus temperature (ρ-T) curves, under DC magnetic fields up to 6 T. The thermally activated flux flow (TAFF) model has been applied in order to calculate the flux pinning energies. The results have shown that the upper critical magnetic field, H c2 (0), and the flux pinning energies vary from ∼113 to 74 T and ∼384 to 101 meV at 0 T, with the Nb-content, respectively. © 2014 Springer Science+Business Media New York.