Improved superconducting properties for multifilament graphene-doped MgB₂ wires by an internal Mg diffusion process

We have fabricated 6 + 1-filament MgB₂ wires using an internal Mg diffusion (IMD) process. For the 3 at% graphene (G) doped long wire with 1.4 mm diameter, the critical current is about 530 A at 4 T, which is 45% higher than that of the undoped sample. Moreover, the G doped wire has higher irreversible strain of 38% in comparison to the undoped one of 30% after 650 °C × 2 h annealing. The obtained results show that the G doped IMD wires with excellent superconductivity and mechanical property can compete with the conventional PIT wires in practical application.