Enhancements of Critical Current Density in the Bi–Pb–Sr–Ca–Cu–O Superconductor by Na Substitution

In this paper, we investigated the influences of Na substitution on the enhancements of critical current density (J(c)) in the Bi-Pb-Sr-Ca-Cu-O (BPSCCO) superconductors. The Bi1.6Pb0.4Sr2Ca2-xNaxCu3O10+delta (where x was ranged from 0 to 0.1) polycrystalline samples were fabricated using solid state reaction technique. The zero electrical critical temperature (T-c) of Na-substituted BPSCCO samples was found to be slightly higher than that of Na-free BPSCCO one. Magnetization J(c) data measured at 65K with field applied parallel to the c-axis of the samples showed that J(c) of Na-substituted BPSCCO samples were enhanced. Possible reasons for the J(c) enhancements were attributed to the effective flux pinning by crystal defects at Ca layers generated by Na substitution. Improvements of volume pinning force (F-p) in terms of magnitude and position of F-pmax were also obtained.