Improved Superconducting Properties by Graphene Doping of Bulk MgB2 Prepared by the Diffusion Method

A study of the effects of graphene doping on the superconducting properties of MgB
₂
bulks prepared by the diffusion method has been conducted over a range of doping levels of 0-30 wt%. The increase in a large quantity of a C-containing nonsuperconducting phase together with the effects of C-substitution on the phase itself results in a change of superconducting properties. While the transition temperature T
_c
monotonically decreases with increasing graphene addition, the critical current density J
_c
is increased for small graphene additions due to the larger volume fraction of the superconducting phase. Larger additions resulted in larger quantities of the nonsuperconducting phase and consequently these samples have a lower Jc.