Boron Purity Effects on Structural Properties of the ${\rm MgB}_{2}$ Obtained by Mg-Reactive Liquid Infiltration

The Mg-Reactive Liquid Infiltration (Mg-RLI) process allows to obtain well densified MgB₂ bulks by using crystalline boron powders up to 100 micron in size: natural liquid Mg percolation within the boron powders preform proceeds for depths of about 50 mm. Much less effective percolation is obtained by using micronic size boron powders, commercially defined "amorphous", of nominal purity of about 96%. The aim of our research is to enlighten the effects of the purity of boron powders as well as of their granularity on the Mg-RLI process. The opportunity of using micronic boron, in order to produce massive superconducting bodies, is particularly appealing due to the low cost of the powders and to the superior superconducting properties of the resulting MgB₂, as it has been already tested.