Formation of ${\rm MgB}_{2}$ Layer Through the Interface Diffusion Reaction in an ${\rm Fe-Mg}\ {\rm alloy}$ / $({\rm B}+({\rm SiC}))$ Composite Tape

The paper proposes a new approach for the fabrication of MgB 2 tape utilizing an interface diffusion reaction between boron (B) and Fe-Mg alloy which has workability to be deformed into a tape form. The composite of an Fe-Mg alloy substrate tape with B layer on its surface was prepared by a dip coating process. During the subsequent heat treatment at 700deg C, Mg in the Fe-Mg alloy substrate diffuses into the coated B layers and reacts with B to form MgB 2 superconducting layer. The reaction proceeds from the Fe-Mg/B interface to the inside of B layer and such a formation mechanism produces a dense structure of MgB 2 with much less MgO impurity, which is difficult to achieve by the conventional PIT process. SiC addition to the B layer is effective at improving the critical current density J c in applied magnetic fields as in the case of the PIT process. A transport J c value of 2,000 A/cm 2 has been obtained at 4.2 K and 4 T for the Fe - 20 at%Mg/(B + SiC) composite tape. This approach is expected to be a breakthrough in the development of MgB 2 wire with a high quality superconducting layer in the composite.