Low-temperature synthesis of MgB2 superconductors

MgB2 superconductors have the outstanding potential to be integrated into diverse commercial applications. However, the critical current density J(c) in MgB2 is still smaller compared with expectations for an optimised material in these applications. Various flux pinning mechanisms are introduced into MgB2 superconductors to improve J(c) by different methods, including irradiation, chemical doping and ball milling. On the other hand, these methods mainly focused on the enhancement of pinning, but always neglect or even worsen the grain connectivity, which limits the further improvement in J(c). Recently, the low-temperature synthesised MgB2 exhibits improved J(c) due to the increases in both the grain connectivity and flux pinning. Ball milling pre-treatment of original powders, usage of different Mg-based precursors and the additions of different metal or alloys are employed to enhance the sintering efficiency of MgB2 at low temperature. Among them, the minor metal or alloy additions are proved to be the most convenient, effective and inexpensive way in accelerating the fabrication of MgB2 superconductors at low temperature. Combining the advantages of metal-activated sintering and carbon doping, it is also proposed that the low-cost MgB2 superconductors with further improved J(c) will be rapidly synthesised at low temperature with metal and carbon-based chemical co-doping.