Evolution of Electromagnetic Properties and Microstructure With Sintering Temperature for ${\hbox {MgB}}_{2}/{\hbox {Fe}}$ Wires Made by Combined In-Situ/Ex-Situ Process

The influences of microstructure, connectivity, and disorder on the critical current density,
J
_c
, are discussed to clarify the different mechanisms of
Jc
(
H
) in different magnetic field ranges for in-situ and combined in-situ/ex-situ MgB
₂
/Fe wires. Sintering temperature plays a very important role in the electromagnetic properties at different temperatures and under various magnetic fields. Connectivity, upper critical field,
H
_c2
, and irreversibility field,
Hirr
, are studied to demonstrate the mechanism of J
_c
dependence on magnetic field. The combined in-situ/ex-situ process is proved to be a promising technique for fabrication of practical MgB
₂
wires.