Influence of Ball-Milled Low Purity Boron Powder on the Superconductivity of ${\rm MgB}_{2}$

MgB2 samples were prepared using as-supplied commercial 96% boron with strong crystalline phase and the same 96% boron (B) after ball milling. The effects of the properties of the starting B powder on the superconductivity were evaluated. We observed that samples using ball-milled 96% B, in comparison with the one made from the as-supplied 96% B, were characterized by small grain size, broadened full width at half maximum (FWHM), and enhanced magnetic critical current density (Jc). Jc reached 2 times 103 A cm-2 at 5 K and 8 T. The improved pinning of these samples seems to be caused by enhanced grain boundary pinning at high field.