Enhanced superconducting properties in bulk MgB2 through spark plasma sintering of ball-milled and sieved crystalline boron

In this study, in situ bulk MgB₂ superconducting samples were sintered using spark plasma sintering (SPS) and characterized through various techniques, including X-ray diffraction (XRD), microstructure evaluation, and magnetization measurements. XRD analysis confirmed that MgB₂ was the primary phase, with a secondary phase of MgO present in the sintered samples. Scanning electron microscopy (SEM) analysis revealed minimal porosity, and the bulk densities reached 95% of the theoretical value for MgB₂, as calculated by mass volume. The samples exhibited remarkably high critical current densities (J_c), up to 405 kA/cm² in self-field at 10 K, representing a 67% improvement over solid-state sintering. These high J_c values are attributed to the enhanced density of the bulk, which increases the superconducting area, which underscores the importance of density enhancement achieved through SPS and the MgB₂ nanograins obtained via ball milling, and sieving of crystalline boron played a crucial role in this improvement.