Pinning behavior of glycine-doped MgB2 bulks with excellent critical current density by Cu-activated low-temperature sintering

Significantly enhanced critical current density in nano-MgB2grains rapidly formed at low temperature with homogeneous carbon doping

“…4b, 4c, and 4d). Even compared to the Cu-doped MgB 2 samples with amorphous boron, or Cu and other carbon-based chemically co-doped MgB 2 samples sintered at low temperature in previous studies [14,[27][28][29], the MgB 2 grains in the samples prepared herein are much smaller (about 100-200 nm, see Fig. 4d) and more homogeneous.…”

“…Moreover, one can also see that the intensity of the first exothermic peak in these carbon-coated samples is stronger than that of a sample made with amorphous boron, accompanied by a decrease in the peaking temperature of the second exothermic peak. The explanation is that carbon-coated amorphous boron is more active than amorphous boron and can better react with solid (see table 1) [24,27,28,32], the level of carbon doping introduced by carbon-coated boron in present work is higher, which must be attributed to the higher activity of the carbon layer on the surface of the boron particles. without Cu addition that was sintered at low temperature is porous, and no regular MgB 2 grains can be easily recognized (see Fig.…”

“…Moreover, the low sintering temperature in the present case can also prevent the MgB 2 grain coarsening that always occurs during high temperature sintering. Especially at high fields, the level of enhancement in J c of these two samples is much higher than those of the Cu and the Cu + nano-SiC co-doped samples, and also other carbon-based chemically doped samples sintered at low temperature [27][28][29]32]. …”

“…This synthesis method is responsible for the significantly improved J c of the present samples compared to MgB 2 samples chemically doped with nano-SiC and other carbon-based dopants, with sintering at either low temperature or high temperature in previous studies [23][24][25][26][27][28][29].…”

Effect of $$\hbox {C}_{4}\hbox {H}_{6}\hbox {O}_{5 }$$ C 4 H 6 O 5 Adding on the Critical Current Density and Lateral Levitation Force of Bulk $$\hbox {MgB}_{2}$$ MgB 2

“…The reason of this difference may be considered of different the experimental route such as sintering temperature, holding time, annealing atmosphere and powder size. It is well known that low J c in MgB 2 is mainly due to the poor grain connectivity with the random and loose packing of MgB 2 grains [19,25,26]. These samples can be clarified as excess malic acid adding due to the high-level malic acid (C 4 H 6 O 5 ) addition with the toluene (C 4 H 7 ) addition.…”