Enhanced flux pinning properties in Bi1.6Pb0.4Sr2−xKxCa2Cu3O10+δ compounds

Abstract

The effect of K substitutions on the structural and superconducting properties of Bi–Pb–Sr–Ca–Cu–O (BPSCCO) system has been investigated. Polycrystalline samples with stoichiometry of Bi1.6Pb0.4Sr2−xKxCa2Cu3O10+δ, where x = (0.00, 0.02, 0.04, 0.06, 0.08, and 0.1), were prepared by using the conventional solid state reaction technique. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) data showed that all samples consisted of high Tc (Bi-2223) and low Tc (Bi-2212) phases, and their volume fractions were found to vary with K content (x). The zero critical temperature was found to decrease from ~ (104.5 to 94.6) K, which was attributed to the decreases in hole carrier concentration. At 65 K, the magnetization critical current density (Jc) of the K-substituted samples was enhanced in comparison with that of the pure one. The Jc enhancement might be attributed to the formation of point defects resulting from the partial substitutions of K into Sr site in the BPSCCO system. In addition, the dominant pinning mechanism was found to be point-like pinning, as described using the Dew-Hughes model.