Improvement in the Crystallographic Phase Content and Superconducting Properties of Mechanically Alloyed MgB₂

In this paper, the results of the superconductivity evaluation of MgB₂ intermetallic-based superconducting materials prepared through mechanical alloying are reported. The formation of the MgB₂ intermetallic phase took place through an intermediate phase reaction at the solid-state reaction temperature, which tends to favor single-phase materials. The annealing of mechanically milled Mg and B powders resulted in the highest mass fraction of MgB₂ observed in this study, reaching more than 90% after annealing at 900 °C for 1 h. At that point, there were still second phases present consisting of Mg, MgO, and Fe₂B. Improved superconducting properties were obtained in samples sintered at temperatures of 850 °C and 900 °C that had a low resistivity, low critical temperature gap values, and a high residual resistivity ratio (RRR).