Synthesis and characterization of excess magnesium MgB2 superconductor under inert carbon environment

The structural, transport and magnetic properties of MgB₂ superconductor heavily blended with Mg is studied. The samples are synthesized with a new approach in both, pressed carbon environment and in flowing argon. The excess magnesium used is observed to play dual role: one being the prevention of Mg losses during the synthesis process and hence maintaining the stoichiometry of MgB₂ phase, and second being the formation of Mg milieu probably all around the MgB₂ grains to give a dense structure. Excess Mg also improves the grain connectivity by going into the pores and there by minimizing the insulating junctions. The residual resistivity of the sample is observed to decrease from 57.02 μΩ cm to 10.042 μΩ cm as it is progressively filled with superconductor–normal–superconductor (SNS) type junctions amongst the grains by the virtue of increased magnesium content. The synthesized samples devoid of porosity show the superconducting transition, T_c in the range of 39–34 K as of clean MgB₂ samples, though overloaded with Mg. The excess Mg resulted in enhanced critical current density, J_c from 6.8 × 10³ A cm^?2 to 5.9 × 10⁴ A cm^?2 at 20 K and 10 kOe, with reasonable decrease in the superconducting transition. Thus our samples being overloaded with Mg impart mechanical strength and competitive superconducting properties, which forms a part of interest.