Improvement of critical current density of MgB 2 bulk superconductor processed by Spark Plasma Sintering

Spark Plasma Sintering (SPS) is a promising rapid consolidation technique that allows a better understanding and optimization of the sintering kinetics and therefore makes it possible to obtain MgB 2 bulk superconductor with tailored microstructures consisting of grains with either spherical or elongated morphology. In this contribution, the role of the precursor powders on the superconducting properties of MgB 2 is investigated. Three sets of bulk MgB 2 material were processed from: (i) a commercially available MgB 2 powder; (ii) a mixture of Mg metal and amorphous B using a single‐step solid‐state reaction process and (iii) a mixture of amorphous boron coated with carbon and Mg metal. The samples were prepared in the same SPS processing conditions. The microstructure of the samples was investigated by X‐ray diffraction, SEM and TEM and correlated to their superconducting properties. The critical current density of the best sample at 20K was J c = 500 kA/cm 2 in self‐field, which is one of the highest critical current density reported for MgB 2 bulk superconductors.