Properties of ${\rm MgB}_{2}$ Tapes Prepared by Using MA In-Ex Situ Powder

MgB2 single-filament tapes and wires with Monel/Nb sheath were produced by the Powder in Tube (PIT)-technique using MA in-ex situ powder. This powder prepared by mechanical alloying (MA) of Mg and B was finally reacted to MgB2 at 700°C. The amount of MgB2 after annealing was about 91 wt%. Additionally 9 wt% MgO secondary phase was found. The primary crystallite size was about 25 nm. Critical current density measurements have shown relatively high values of Jc = 104 A/cm2 at 6.7 T for unsintered tapes in parallel magnetic field. Heat treatment at temperatures of up to 900°C could not improve these values, probably due to MgO hindering the sintering process.