High Critical Current Density and Improved Irreversibility Field in Bulk   MgB2 Made By A Scaleable, Nanoparticle Addition Route
  Bulk samples of MgB2 were prepared with 5, 10, and 15% wt.% Y2O3 nanoparticles added using a simple solid-state reaction route. Transmission electron microscopy (TEM) showed a fine nanostructure consisting of ~3-5 nm YB4 nanoparticles embedded within MgB2 grains of ~400 nm size. Compared to an undoped control sample, an improvement in the in-field critical current density Jc was observed, most notably for 10% doping. At 4.2K, the lower bound Jc value was ~2x105A.cm-2 at 2T. At 20K, the corresponding value was ~8x104A.cm-2. Irreversibility fields were ~11.5 T at 4.2K and 5.5T at 20K, compared to ~4T and ~8T, respectively, for high-pressure synthesized bulk samples. 
J. Wang, Y. Bugoslavsky, A. Berenov, L. Cowey, A.D. Caplin, L.F.   Cohen, J.L. MacManus Driscoll, L. D. Cooley, X. Song, D. ...