Significant enhancement of critical current density in Gly-doped MgB ₂ bulk by tailoring the formation of MgO

A significant enhancement of critical current density (J _c) was obtained in MgB ₂ + 3 wt.% glycine samples with a large amount of MgO. The improvements in J _c and in the irreversible magnetic field (H _irr) are attributed to the pinning effects of high C-substitution level, nanoscale MgO, and to the even boundaries of small grains. This doping method overcomes the degradation of J _c under a low field in previously reported SiC-doped samples. Moreover, the formation of MgO was demonstrated to be the result of the reactions between Mg, CO ₂ and O ₂.