Improved Current Densities in MgB2 By Liquid-Assisted Sintering
  Polycrystalline MgB2 samples with GaN additions were prepared by reaction of Mg, B, and GaN powders. The presence of Ga leads to a low melting eutectic phase which allowed liquid phase sintering and produces plate-like grains. For low-level GaN additions (5% at. % or less), the critical transition temperature, Tc, remained unchanged and in 1T magnetic field, the critical current density, Jc was enhanced by a factor of 2 and 10, for temperatures of \~5K and 20K, respectively. The values obtained are approaching those of hot isostatically pressed samples. 
S. K. Chen, Z. Lockman, M. Wei, B. A. Glowacki and J. L.   MacManus-Driscoll