Preparation of MgB2 tapes using a nanocrystalline partially reacted precursor

Fe-cladded MgB2 conductors have been prepared by the powder-in-tube method using mechanically alloyed nanocrystalline Mg+2B powder mixtures consisting of the constituents Mg, B, and MgB2 as precursor. Despite low T-c values of about 31 K, maximum critical current densities (J(c)) of 22 and 7 kA/cm(2) in external magnetic fields of 7.5 and 10 T, respectively, are achieved at 4.2 K. These excellent values can mainly be attributed to the very fine-grained microstructure of the superconducting phase. Higher values have only been reported for tapes doped with SiC nanoparticles. The irreversibility fields H-irr of these tapes are 9.5 and 4.2 T at 10 and 20 K, respectively. (C) 2003 American Institute of Physics.