The doping of MgB2 precast material with 2 at.% and 5 at.% TaB2 under varying high energy processing ball milling conditions with Pulverisete-4 and Spex mills was carried in order to investigate critical current enhancement condition. Higher critical current densities were achieved with the 5 at.% TaB2-doped MgB2 than with the 2 at.% doped MgB2. The measurements showed that maximum critical current densities were 398.8 kA/cm2 and 474.1 kA/cm2 (both measured at 2 Tesla fields) for the Spex mill for 2 at.% and 5 at.% doping respectively. Corresponding to the same time of milling, the Pulverisette-4 mill operated at 800 rpm yielded materials with critical current densities of 305 kA/cm2 and 295 kA/cm2 corresponding to 2 at.% and 5 at.% doping respectively. These results demonstrated that dopant level contribution to critical current density enhancement was more significant than the effects of the ball milling engendered by the ball mills.
Effect of TaB2 doping on the current density of MgB2.