Development in processing of MgB₂ cryo-magnet superconductors

Spark Plasma Sintering is a promising rapid consolidation technique that allows a better understanding and manipulating of sintering kinetics and therefore makes it possible to obtain MgB₂-based ceramics with tailored microstructures. Commercial MgB₂ powders were spark plasma sintered with an applied mechanical pressure, leading to MgB₂ pellets with 99% relative density. The obtained samples show a sharp superconducting transition with an onset at 38.5 K. The critical current density was measured equal to 5.6 × 10⁴ A/cm² at 20 K under 1 T applied field. Otherwise, the trapped field was also investigated. A 5 mm thick pellet with a 20 mm diameter prepared with optimized processing temperature demonstrated a trapped field of 1.2 T at 15 K and up to 2.5 T at 10 K.