A Trapped Field of >3T in Bulk MgB2 Fabricated by Uniaxial Hot Pressing

TL;DR

This study demonstrates that uniaxial hot pressing can produce dense MgB2 superconductors capable of trapping magnetic fields over 3 Tesla at 17.5 K, highlighting potential for scalable high-field applications.

Contribution

It introduces a scalable uniaxial hot pressing method to fabricate dense MgB2 with high trapped fields, and links performance limits to flux pinning rather than connectivity.

Findings

Achieved >3 T trapped field at 17.5 K in MgB2 bulk.

Critical current density aligns with local measurements, indicating flux pinning limits.

Suggests increasing size and doping to enhance trapped field performance.

Abstract

A trapped field of over 3 T has been measured at 17.5 K in a magnetised stack of two disc-shaped bulk MgB2 superconductors of diameter 25 mm and thickness 5.4 mm. The bulk MgB2 samples were fabricated by uniaxial hot pressing, which is a readily scalable, industrial technique, to 91% of their maximum theoretical density. The macroscopic critical current density derived from the trapped field data using the Biot-Savart law is consistent with the measured local critical current density. From this we conclude that critical current density, and therefore trapped field performance, is limited by the flux pinning available in MgB2, rather than by lack of connectivity. This suggests strongly that both increasing sample size and enhancing pinning through doping will allow further increases in trapped field performance of bulk MgB2.