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

This study refers to Rare-Earth elements (
${\rm RE}={\rm Ce}$
, Sm, Gd) doping of
${\rm MgB}_{2}$
bulk materials. The synthesis of doped
${\rm MgB}_{2}$
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
${\rm MgB}_{2}$
crystal lattice or the growth of intergrain boride phases of nanometric size that modify the grain boundaries of the
${\rm MgB}_{2}$
polycrystals. The structure of the resulting RE-doped
${\rm MgB}_{2}$
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
${\rm MgB}_{2}$
have been measured by magnetization loops.