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A significant enhancement of critical current density (J c) was obtained in MgB2 +3wt.% 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, CO2 and O2. [ABSTRACT FROM AUTHOR]

Lamellar MgB2 grains were synthesized by Cu-activated sintering at low temperature. We found that the Mg–Cu liquid can provide a constant liquid environment and the formation of lamellar MgB2 grains is attributed to the two-dimensional nucleation and growth mechanism in the liquid–solid interface. According to the analysis on the temperature dependence of resistivity, these lamellar MgB2 grains possess much better grain connectivity than the typical morphology of MgB2 grains synthesized by the traditional solid-state sintering. [Copyright &y& Elsevier]

Multi-doped MgB2 superconductors with excellent critical current density (Jc ) were rapidly synthesized by low-temperature activated sintering with Cu addition as the activator and nano SiC addition as the carbon-based chemical. Combined with microstructure observation and flux pinning force analysis, it is found that the enhancement of Jc (especially at low field) was mainly attributed to the higher density, lower crystallinity and the concentration of Cu activator around the sintered voids. [Copyright &y& Elsevier]