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 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 J_C was observed, most notably for 10% doping. At 4.2 K, the lower bound J_C value was ∼2×10⁵ A cm^-2 at 2 T. At 20 K, the corresponding value was ∼8×10⁴ A cm^-2. Irreversibility fields were 11.5 T at 4.2 K and 5.5 T at 20 K. © 2002 American Institute of Physics.