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We have successfully fabricated single-filament composite MgB2/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, Ic∼316 A and ∼105 A were observed at T=4.2 K with H=0 G for as-rolled and sintered MgB2/SS tapes, respectively. In addition, the isothermal magnetizations M(H) of sintered MgB2/SS tapes and commercial MgB2 powder were measured at temperatures T between 5 and 50 K in fields up to 6 T, employing a PPMS. The critical current density (Jc) values obtained from the M(H) data, using Bean model, were >5 × 105 A/cm2 and >5 × 107 A/cm2 at T=10 K with H=0 G for the sintered MgB2/SS tapes and the commercial MgB2 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 MgB2 and SS tube was found in the SEM/EPMA. However, traces of reaction can be seen in the interface region between MgB2 core and SS tube for the sintered MgB2/SS tapes, from the EPMA line profiles. In addition, impurity phases such as MgO or MgB4, which can be generated inside the superconductor MgB2 core during fabrication, were observed by XRD analyses.
Date of Publication: June 2003