Properties of MgB2 wires made of oxidized powders

Single-core MgB2/Ti wires have been made from mixed (in situ) and intensively milled (mechanically alloyed) Mg + B powders. Both powders were oxidized at room temperature for 48 h and also by heat treatment at 400 °C/1 h in air. Critical current density and resistivity measurements were performed for the samples with oxidized powders and also for those protected in glove box with high purity Ar. It was found that oxidation of in situ mixture is slightly decreasing critical current density. Surprisingly, the oxidation of much finer mechanically alloyed powder is improving Jc in spite of increased MgB2 resistivity. Jc at 10T increase by 47–100% was measured for mechanically alloyed powder oxidized at room temperature. This allows a safety handling with intensively milled Mg + B powders in air.

► Mixed and intensively milled Mg + B powders differently oxidized in air were used for MgB2 wires.
► The effect of created MgO on resistivity and transport current flow in MgB2 was studied.
► Improved critical currents were obtained for oxidized intensively milled fine-grain Mg + B powder.
► The effect of fine grain and uniformly distributed MgO is considered for pinning improvement.
► Safety handling of intensively milled Mg + B powders in air is discussed.