Abstract

The effects of nano Fe_xC addition to superconducting properties of in situ processed MgB_2 superconductors was examined. 0.1 wt.% and 1 wt.% nano Fe_xC powders were mixed with boron and magnesium powders by ball milling. The powder mixtures were made into pellets by uniaxial pressing. The pellets were heat-treated at 700°C-900°C in argon atmosphere for MgB_2 formation. It was found by powder X-ray diffraction that the raw powders were completely converted into MgB_2 after the heat treatment. The superconducting transition temperature (T_c) and critical current density (J_c), estimated from susceptibility-temperature and M-H curves, were decreased by nano Fe_xC addition. The T_c and J_c decrease by nano Fe_xC addition are attributed to the incorporation of iron and carbon with MgB_2 lattices (Fe substitution for Mg and C substitution for B) due to the high reactivity of the nano Fe_xC powder.

• Keywords: Nano Fe_xC;MgB_2;Critical current density;Superconducting temperature;