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 J_c 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.