Design and characterisation of ex situ bulk MgB2 superconductors containing a nanoscale dispersion of artificial pinning centres

The oxide dispersion strengthened (ODS) concept was applied to commercial MgB₂ poweder and Y₂O₃ nanopower, rather than the established stells and superalloys.

After mechanically alloying in a high energy planetary ball mill and consolidating using the field assisted sintering technique, the composite powders were ball milled for different times, up to 12 hours, and characterised using particle size analysis, x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM).

The microstructure and superconducting properties were characterised by density, XRD and STEM and magnetic property measurements.  The powder microstructure comprised Y₂O₃ particles dissolved into the MgB₂ matrix, and after consolidation there was a near-uniform dispersion of precipitated YB₄ and MgO particles.

A bulk 0.5 wt% Y₂O₃-MgB₂ composite showed the best superconducting performance with a significant improvement in J _c at high field, compared with unmodified MgB₂, and only a small reduction in T _c.  

The results suggest that the ODS concept is promising to improve the superconducting properties of MgB₂.