CrB2 Doping Effects on Critical Current Density and Flux Pinning of MgB2

A series of polycrystalline bulk samples of (MgB
₂
)
_1-x
(CrB
₂
)
_x
with 0 ≤ x ≤ 10% were synthesized by a two-step solid-state diffusion reaction. Crystal structure, microstructure, superconductivity, and flux pinning behavior were investigated. The CrB
₂
dopant was found to significantly depress superconductivity by substituting Mg with Cr. In addition, a portion of the unreacted CrB
₂
appears as nanoparticle impurities inserted into the MgB
₂
matrix, which enhances flux pinning. As a result, the critical current density of the (MgB
₂
)
_1-x
(CrB
₂
)
_x
sample was significantly improved at low doping levels.