Enhancement of grain connectivity and critical current density in the ex-situ sintered MgB2 superconductors by doping minor Cu

Abstract

The influence of Cu addition on the microstructure and superconducting performance of ex-situ sintered MgB2 is systemically studied. It is found that the critical current density (Jc) of the Cu-doped sample is improved compared to the un-doped samples. In particular, the Jc of the Cu-doped sample sintered at 900 °C for only 10 min is the best value at low fields. The reason is that Cu addition can obviously promote the decomposition of MgB2: MgB2↔MgB4+Mg, which produces more Mg that can then react with Cu, forming local Mg-Cu liquid at high temperature. The presence of this local Mg-Cu liquid can significantly enhance the migration and self-sintering of MgB2, leading to the significant improvement in the grain connectivity and Jc. Our results indicate that Cu addition is a promising method to fabricate high-performance ex-situ MgB2 bulks and wires.