Processing and Characterization of Charcoal Added Bulk MgB₂ Superconductor

In this study, we focus on methods to further improve the flux pinning and critical current density (J _c) of disk shaped MgB₂ bulk superconductors by a comparative study with locally obtained charcoal at optimized processing conditions. The doping of charcoal was varied at 0, 0.2, 0.4 and 0.6 wt%. Bulk MgB₂ samples were produced by in-situ solid state reaction in Ar gas and ambient pressures at 775 °C, employing high purity of Mg metal and nano B powder mixed in a fixed ratio of Mg:B = 1:2 and optimal conditions. The phase has been investigated by X-ray diffractometer (XRD). The effects of the dopants on superconducting properties especially the field dependence of J _c have been determined by superconducting quantum interference device (SQUID) and critical temperature (T _c). Measurements of the magnetic susceptibility showed sharp superconducting transitions (ΔT _c ∼ 1 K). J _c at self-field and 20 K was determined to be ∼280 and 467 kA/cm² for the 0 and 0.4 wt% charcoal added samples respectively. The structural and superconducting results were correlated with the addition of charcoal in the final product.