Improvement in electrical properties of Bi-2212 superconducting materials substituted with large-scale nano-sized tin
Mehmet Ersin Aytekin, Mustafa Akyol, Berdan Özkurt
Abstract
Abstract 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.