The effects of nano-scale iron doping on superconductivity and microstructure of MgB2 bulk

Mg
_1-x
Fe
_x
B
₂
superconductor was prepared by in situ solid state reaction to study the effects of nano-iron doping on the superconductivity of MgB
₂
. Two kinds of nano-iron sources were used: nano-iron particles and nano-iron wires. It was found that crystal structure was not affected by nano-iron doping for either form of dopant source. T
_c
, J
_c
, and H
_irr
were severely suppressed by iron nano-particles doping. In contrast, with iron nano-wires doping, T
_c
of the MgB
₂
superconductors were not changed remarkably, while their J
_c
and H
_irr
were slightly enhanced at all the temperature ranges investigated in this work. Under 4 T field, the sample doped with 1% wt iron nano-wires reached the highest J
_c
of 1.1 times 10
⁴
A/cm
²
at 10 K and 2.2 times10
²
A/cm
²
at 20 K, respectively. It was argued that the Fe nano-wires may be introduced into MgB
₂
as external pinning centers in high field region.