In this study, we investigated the effect of Mg adding into bulk MgB₂ superconductors on their superconducting properties. Highly dense bulk MgB₂ samples were prepared by unconventional "Spark Plasma Sintering" (SPS). Different precursors were used: i) the commercial powder MgB₂ and ii) mixtures of magnesium and nano boron powder (Mg + 2B) for an "in-situ" reactive synthesis. The amount of Mg added was 0.5, 1, 3 and 15wt% of 1.5g MgB₂ powder. The density of the obtained MgB₂ bulks was up to 99 % of the theoretical density of the material, which is the highest so far reported in literature. Then structural and microstructural characterizations were carried out with these samples and correlated to their superconducting properties, in particular their critical current densities (J_c) measured at 20 K. A high J_c = 675 kA/cm² was obtained in self-field. Remarkably for a bulk MgB₂, J_c was above 10kA/cm² at 4T.

Keywords: MgB2