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

haadf images and corresponding y and o edx maps of 2 wty2o3 mgb2 powder ball milled for 10 min 1 and 12 h

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.