Fabrications and properties of MgB/sub 2//stainless-steel tapes by PIT process

Abstract

We have successfully fabricated single-filament composite MgB/sub 2//Stainless-Steel (SS) tapes using powder-in-tube processes such as swaging and cold rolling. The transport critical currents, that were measured by a standard dc four-probe method, I/sub c//spl sim/316 A and /spl sim/105 A were observed at T=4.2 K with H=0 G for as-rolled and sintered MgB/sub 2//SS tapes, respectively. In addition, the isothermal magnetizations M(H) of sintered MgB/sub 2//SS tapes and commercial MgB/sub 2/ powder were measured at temperatures T between 5 and 50 K in fields up to 6 T, employing a PPMS. The critical current density (J/sub c/) values obtained from the M(H) data, using Bean model, were >5 /spl times/ 10/sup 5/ A/cm/sup 2/ and >5 /spl times/ 10/sup 7/ A/cm/sup 2/ at T=10 K with H=0 G for the sintered MgB/sub 2//SS tapes and the commercial MgB/sub 2/ powder, respectively. On the other hand, we investigated the cross sections of both the sintered and the as-rolled tapes, using SEM and EPMA. No evidence of significant diffusion between MgB/sub 2/ and SS tube was found in the SEM/EPMA. However, traces of reaction can be seen in the interface region between MgB/sub 2/ core and SS tube for the sintered MgB/sub 2//SS tapes, from the EPMA line profiles. In addition, impurity phases such as MgO or MgB/sub 4/, which can be generated inside the superconductor MgB/sub 2/ core during fabrication, were observed by XRD analyses.