The effects of nano-scale iron doping on superconductivity and microstructure of MgB2 bulk

Mg1−xFexB2 superconductor was prepared by in situ solid state reaction to study the effects of nano-iron doping on the superconductivity of MgB2. Two kinds of nano-iron sources were used: nano-iron particles and nano-iron wires. It was found that crystal structure was not affected by nano-iron doping for either form of dopant source. Tc, Jc, and Hirr were severely suppressed by iron nano-particles doping. In contrast, with iron nano-wires doping, Tc of the MgB2 superconductors were not changed remarkably, while their Jc and Hirr were slightly enhanced at all the temperature ranges investigated in this work. Under 4 T field, the sample doped with 1 % wt iron nano-wires reached the highest Jc of 1.1×10⁴ A/cm² at 10 K and 2.2×10² A/cm² at 20 K, respectively. It was argued that the Fe nano-wires may be introduced into MgB2 as external pinning centers in high field region.