Improvement in electrical properties of Bi-2212 superconducting materials substituted with large-scale nano-sized tin

In the current work, the effect of nano-sized Sn (50 nm)/Sr partial replacement on the superconducting properties such as crystal structure, quality of intra- and intergrain boundary coupling, dc electrical resistivity, and dc magnetization in the Bi-2212 ceramic superconductors were investigated. Ceramic superconductors with nominal composition of Bi${}_2$Sr${}_{2-x}$(Sn)${}_x$Ca${}_1$Cu${}_{1.75}$Na${}_{0.25}$O${}_y$ where x = 0.25, 0.30, 0.35 and 0.40 were prepared by solid-state reaction method and characterized by powder X-ray diffraction (XRD), dc electrical resistivity, scanning electron microscopy (SEM) and magnetic hysteresis (M-H) measurements. Phase examination of by XRD indicated that the doping of x = 0.25 ratio nano-sized SnO${}_2$ to the strontium sites improved the formation of the Bi-2212 high-temperature superconducting phase. SEM micrographs showed that the morphological structure of all samples consisted of plate-like grains, which were separated from each other by grain boundaries, indicating the Bi-2212 superconducting phase. The highest superconductivity transition temperature among the samples was measured as the T${}_c$${}^{onset}$ = 86 K at x = 0.25 in Bi${}_2$Sr${}_{2-x}$(Sn)${}_x$Ca${}_1$Cu${}_{1.75}$Na${}_{0.25}$O${}_y$. M-H loops of the Bi${}_2$Sr${}_{2-x}$(Sn)${}_x$Ca${}_1$Cu${}_{1.75}$Na${}_{0.25}$O${}_y$ sample at x = 0.25 ratio is larger compared to other examples, indicating improvement intergrain connectivity as well as enhanced flux pinning centers. In addition, the critical current (J${}_c$) values of the samples were calculated from M-H measurement using Bean's critical current model. The best J${}_c$ values were obtained as 570 A/cm${}^2$ at 15 K, which is a relatively high value for BSCCO superconductors with polycrystalline structure.