Borax addition in the MgB2 bulk system

MgB2 bulk samples with different borax additions, x = 0.0, 4.42, 13.55, 23.06 wt% were fabricated using solid state sintering. XRD measurements reveal the increasing MgO presence and broadening of the (100) MgB2 peak as the borax concentration increased. Granular morphology was observed for all samples which are characteristic to MgB2. Based on the SEM analysis, sintering necks appear in the pristine sample which are not present in the borax-added bulks. Diamagnetic transition was detected for samples with additions up to 13.55 wt%. Susceptibility measurements reveal the transition width is not sharp for x = 13.55 wt% addition, an indication of poor grain coupling due to large impurity volume while no diamagnetic signal was observed for x = 23.06 wt% borax addition.