Large transport critical currents in dense Fe- and Ni-clad MgB2 superconducting tapes

We report on the preparation of dense monofilamentary MgB2/Ni and MgB2/Fe tapes with high critical current densities. In annealed MgB2/Ni tapes, we obtained transport critical current densities as high as 2.3×105 A/cm2 at 4.2 K and 1.5 T, and for MgB2/Fe tapes 104 A/cm2 at 4.2 K and 6.5 T. An extrapolation to zero field of the MgB2/Fe data gives a critical current value of ∼1 MA/cm2, corresponding to a critical current value well above 1000 A. The high jc values obtained after annealing are a consequence of sintering densification and grain reconnection. Fe does not react with MgB2 and is thus an excellent sheath material candidate for tapes with self-field jc values at 4.2 K in excess of 1 MA/cm2.