Very fast formation of superconducting MgB2/Fe wires with high J(c)

In this paper, we have investigated the effects of sintering time and tempe rature on the formation and critical current densities of Fe-clad MgB2 wire s. MgB2 wires were fabricated using the powder-in-tube process and sintered for different periods of time at predetermined temperatures. All the sampl es were examined using XRD, SEM, and magnetisation measurements. In contras t to the common practice of sintering for several hours, the present result s show that there is no need for prolonged heat treatment in the fabricatio n of Fe-clad MgB2, wires. A total time in the furnace of several minutes is more than enough to form nearly pure MgB2 with high performance characteri stics. The results from T-c,J(c) and H-irr show convincingly that the sampl es which were sintered for 3 min above 800 degreesC are as good as those si ntered for longer times. In fact, the J(c) field performance for the most r apidly sintered sample is slightly better than for all other samples. J(c) of 4.5 x 10(5) A/cm(2) in zero field and above 10(5) A/cm(2) in 2 T at 15 K has been achieved for the best Fe-clad MgB2 wires. As a result of such a s hort sintering there is no need for using high purity argon protection and it is possible to carry out the heat treatment in a much less protective at mosphere or in air. These findings substantially simplify the fabrication p rocess, making it possible to have a continuous process for fabrication and reducing the costs for large-scale production of MgB2 wires. (C) 2001 Else vier Science B.V. All rights reserved.