Enhancement of critical current density in glycine-doped MgB2 bulks

Samples of MgB2 + x wt% glycine (with x = 0, 2, 5 and 8) were sintered at 800 °C for 30 min. Obvious enhancement of critical current density (Jc) over the entire field was obtained in 5 wt% glycine-doped sample, indicating that grain connectivity and pinning effect were both improved. The improvement of Jc was attributed to the pinning effect by C substitution, MgO nano-particles, and relatively smaller MgB2 grains. Besides, 2 wt% glycine could only improve Jc at low field, while excessive glycine (above 5 wt%) would lead to unfavorable Jc performance.

► Carbon doping can be realized by glycine doping.
► Enhancement of critical current density over the entire field was obtained in 5 wt% glycine-doped sample.
► Glycine played a role in both grain refinement and introducing pinning effect.