Analysis of Various Dopants on the ${\rm MgB}_{2}$ Superconducting Properties

The doping of MgB₂ superconductor has been approached with the addition of carbon atoms into the boron sites and metallic elements (i.e. Zn,Cu,Co) into the MgB₂ lattice. Here we use the Mg-Reactive Liquid Infiltration process in an attempt to promote the dopant insertion, either by using Mg based alloys and mixing the dopants (i.e. nano-size SiC in the case of C doping) with the boron powders. The efficiency of the MgB₂ crystal lattice doping via the infiltration process is monitored by measuring the lattice parameters variation by X-ray diffraction and by microanalytical fluorescence scanning spectroscopy. The superconducting properties have been measured magnetically at high fields and at various temperatures, up to about the critical temperature. The magnetization cycles have shown a substantial increase of the irreversibility field, B _irr, with doping. The performances of the MgB₂ with different dopants are compared and discussed.