Large critical current density in MgB2 wire using MgB4 as precursor

A high-purity MgB4 phase has been synthesized and used as the precursor powder for the realization of in situ wires. Various final heat treatments, from 550 to 1100 ° C for 20 min each, have been carried out to convert the inner mixture to MgB2. Critical current densities up to 1.75 × 106 and 0.98 × 106 A cm−2 at 4.2 and 20 K, with 0.2 T, up to 0.76 × 105 A cm−2 at 4.2 K and 4 T, and up to 0.78 × 105 A cm−2 at 20 K and 2 T were measured. Critical temperatures up to 38.5 K were measured. These results suggest that this could be a good alternative to both ex situ and classical in situ routes.