${\rm MgB}_{2}$ Doping by Rare-Earth Metals and Borides

This study refers to Rare-Earth elements (RE = Ce, Sm, Gd) doping of MgB₂ bulk materials. The synthesis of doped MgB₂ has been performed by Reactive Liquid Mg Infiltration process (Mg-RLI): the RE additives, in the form either of pure metallic powder or of borides powder, have been mixed with the starting boron powder. The RE dopants could operate through two different doping mechanisms: the substitution of Mg ions in the MgB₂ crystal lattice or the growth of intergrain boride phases of nanometric size that modify the grain boundaries of the MgB₂ polycrystals. The structure of the resulting RE-doped MgB₂ has been characterized by X-ray diffraction and SEM/EDS analysis. The effects of this kind of doping on the high magnetic field properties of MgB₂ have been measured by magnetization loops.