Thermally stabilized MgB2 composite wires with different barriers

Glidcop sheathed in situ MgB2 wires with Nb and Ti barriers and Cu and Al inner cores have been made and tested. It was found that the inner aluminium stabilization is not appropriate, due to a reaction with Nb during the heat treatment at 630 °C. Using Ti barriers, much higher Jc values were obtained when compared to Nb barriers. The enhancement by 1.5 to 2.1 times is explained by the absorption of impurities from MgB2 filaments by titanium. On the other hand, Ti reacts with copper and reduces the conductivity of metallic sheath (RRR ratio), which affects the thermal stabilization of the MgB2 wire.

► We examine MgB2 wires with Nb and Ti barriers and Cu and Al inner cores.
► Aluminium core is not suitable for stabilization due to reaction with Nb at 630 °C.
► Ti barrier wire gives much higher Jc in comparison to Nb barrier wire.