Fabrication and Characterization of Al-Doped MgB2 Superconducting Bulks

Abstract

In this study, Al-doped MgB₂ bulks with different doping levels (Al contents of 1-5 at% ) were fabricated by a ball-milling process followed by spark plasma sintering in order to improve the current density of MgB₂ by doping especially at elevated magnetic fields. The microstructure and superconducting properties of the MgB₂ before and after sintering were investigated. It was found that the particle size of Al reduces through the ball-milling process, and the small Al particles gradually dissolve into MgB₂ powder, changing the lattice parameters of the MgB₂ structure. The Al-doped-MgB₂ bulks showed remarkably improved connectivity, higher density and lower MgO impurity compared to the undoped MgB₂ with reasonably high critical current density (∼338 kAcm ^-2 at 1 T and 20 K). Al doping led to an enhancement in the critical current density without significant reductions in transition temperature.