Synthesis and Characterization of Carbon-Doped MgB2 Superconductor Under Inert Carbon Environment

A systematic study on the synthesis of carbon-doped MgB2 superconductor, using a new approach wherein the sample was treated under both pressed carbon environment as well as flowing argon, is presented. The sample synthesized was found to be compact and showed cannibalistic surface morphology. Carbon doping in the sample, crystallized in hexagonal structure, accounted for the reduced in-plane lattice parameter of 3.06 A. The intraband scattering due to doping of carbon resulted in a decreased superconducting transition at about 29 K. The behavior of resistivity with respect to a decrease in temperature was embedded in the signatures for the scattering of electrons by phonons as well as the grain boundary impurity in the sample. The carbon doping achieved by the proposed synthesis technique showed improvement in the self-field critical current density up to around 105 A/cm2 at 5 K. The flux-pinning plots were studied to understand the dominant pinning mechanism in the sample.