Investigation of the effects of high valency nb substituted to the copper site on superconductive properties in Bi1.6Pb0.4Sr2Ca0.925Na0.075Cu2O8+δ ceramic superconductor

In this study, the effects of high-valent Nb addition to the copper (Cu) site on the superconductivity properties of Bi1.6Pb0.4Sr2Ca0.925Na0.075Cu2-xNbxO8 (x= 0, 0.05, 0.075, 0.10, 0.15 and 0.20) system prepared by the classical solid state reaction method are investigated.. As a result of XRD analysis, although the main phase is Bi-2212 in all samples, small diffraction patterns of Bi-2201 and Bi-2223 phases were also observed. In addition, the lattice parameters of the samples decreased with the addition of Nb. Randomly oriented platelet-like and occasionally needle-like grains were observed from SEM images. Symmetrical M-H curves specific to type superconductors were obtained at the temperatuees of 10, 20, and 30 K, for all samples. The permanent magnetization values (Mr), which is a measure of the pinning abilities, increased with the Nb-subsitution. Likewise, the critical current densities (Jc) values of the samples also increased with the Nb content. As a result, Nb addition is a useful method in terms of improving the superconducting properties of the Bi1.6Pb0.4Sr2Ca0.925Na0.075Cu2-xNbxO8 system.