Enhancement of critical current density in low level Al-doped MgB₂

The effect of nanoscale Fe doping on the superconducting properties of MgB2

“…Because of the large coherence length of MgB 2 many nano-particles at grain boundaries do not cause weak links but act as effective pinning centres which has been well demonstrated by a number of doping studies [7,[9][10][11][12][13][14][15]. In the case of Fe doping, FeB particles at grain boundaries cause grain decoupling because FeB particle scattering affects a much larger volume surrounding the particle than nonmagnetic particles.…”

SiC and carbon nanotube distinctive effects on the superconducting properties of bulk MgB2

“…[1][2][3][4][5][6] On the other hand, the doping level affects the interband scattering coefficients ⌫ , ⌫ and the diffusivity of each band D , D , as predicted by Gurevich et al, [7][8][9][10][11] and these changes may cause a significant H c2 variation. Earlier attempts succeeded in raising the intragrain J c through the incorporation of Mg͑B 1−x O x ͒ 2 , 1 SiC, 2,12,13 Al, 3 Dy 2 O 3 , 4 nano-C, 5 and carbon nanotubes, 6,12,[14][15][16] which produce a decrease in the critical temperature ͑T c ͒ by chemical substitution and probably lattice strain. 17 The improvement of intergrain J c in bulk samples is related to grain connectivity 18 and may be achieved by optimizing the processing parameters ͑i.e., ultrasonication, 16 HIPing, 18 applying magnetic field during the sintering process, 19 etc.͒.…”

Variation of pinning mechanism and enhancement of critical current density in MgB2 bulk containing self-generated coherent MgB4 impurity

“…Variation of pinning mechanism and enhancement of critical current density in MgB 2 bulk containing self-generated coherent MgB 4 2 , with self-generated MgB 4 pinning centers, have experienced two-step sintering process, initially at 750 C and then 900-1000 C. On the contrary to the widely accepted point that MgB 4 deteriorates superconductivity, it was found that MgB 4 played a significant role in enhancing critical current density. The precipitation pattern of MgB 4 was studied from the lattice scale images.…”

“…High temperature will lead to an increasing particle size of MgB 4 , even larger than the coherent length of MgB 2 , as in sample S750-1000 (see Fig. 2(d)).…”

“…2 A series of exciting achievements in improving the J c performance have been made by chemical doping method, which has been considered as the most convenient and effective way, owing to the dopant's talents in introducing extra electrons or second-phase particles. 3,4 For example, carbon-containing compound addition, originating from C substitution for B sites in the lattice, would induce the lattice distortion and the devotion of one more electron, and thus enhance the J c . Elements Cu and Y addition would improve the J c performance of MgB 2 by forming nano-sized MgCu 2 and YB 4 second phases with Mg and B, respectively.…”