Impact of silver addition on the superconducting performances of Bi2Sr2Ca0.925Na0.075Cu2Oy:Ag composite fibers

Abstract

This work studies the impact of metallic Ag addition on the microstructural, electrical, superconducting, and magnetic properties of Bi2Sr2Ca0.925Na0.075Cu2Oy. Samples with 0, 1, 3, 5 wt% were prepared from precursors produced by sol-gel method, followed by texturing through the laser floating zone (LFZ) technique. The normal state and residual resistivity values decrease with Ag addition up to 3 wt% (from 7.61 to 2.54, and from 1.85 to 0.25 mΩ.cm, respectively), reflecting the reduction of porosity and the improvement of grains alignment and connectivity. Irreversibility line (IL) shifts towards high temperature with the introduction of Ag, confirming the higher grains connectivity in Ag-containing samples. Moreover, the increase of Hirr (from 28.9 to 43.1 T), Hc2 (from 64.6 to 85.9 T), and Jc (from 4x104 to 1.2x105 A/cm2) values with Ag addition also point out to the improvement of grains connectivity and flux pinning energies induced by Ag addition.