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

抄録

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 Bi_1.6Pb_0.4Sr₂Ca_2−xNa_xCu₃O_10+δ (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 65 K 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.