Effect of SiO₂and SiC doping on the powder-in-tube processed MgB₂tapes

Abstract

Effect of SiO 2 and SiC nano-powder doping was investigated for the powder-in-tube processed MgB 2 /Fe tapes. Mg or MgH 2 powder was used as the Mg source of starting materials, and heat treatment was carried out at 600 • C for 1 h. These heat treatment conditions of lower temperature and shorter heating time are advantageous from the aspect of practical production processes. MgH 2 powder improved the connection of MgB 2 grains and prevented oxidation of MgB 2 . SiC and SiO 2 doping greatly enhanced the critical current density (J C ) values of the tapes prepared with Mg + B powder. However, only the SiC doping was effective in enhancing J C values for MgH 2 + B powder. SiC doping decreased magnetic field sensitivity of J C , while SiO 2 doping did not change the field dependence of J C . The SiC doped tape showed transport J C value of about 6 500 A cm −2 at 4.2 K and in the magnetic field of 12 T. The irreversibility field increased from 17 T to 23 T by the SiC doping.

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.…”

The effect of doping level and sintering temperature on Jc(H) performance in nano-SiC doped and pure MgB2 wires

“…The exceptional properties of SiC as a dopant have been verified by a number of groups over the past few years. [7][8][9][10][11][12][13][14][15][16][17][18] However SiC doping was found to have some negative effect on J c in the low field region. The J c for SiC doped MgB 2 was lower than that for undoped MgB 2 below 4 T at 5 K and below 2.5 T at 20 K. 2,13,17 There are many applications in the low field region such as in open magnetic resonance imaging ͑MRI͒ transformers and electric cables which normally operate at around 1-3 T. Thus it is important that the enhancement of J c by SiC doping can be extended to include all the field regions.…”

Role of carbon in enhancing the performance of MgB2 superconductor

“…On the other hand, the relatively larger ξ of MgB 2 (about 5-10 nm) allows optimum pinning by nparticles for enhancement of the J c (H) performance. Although this effect has been studied for a variety of different nano-particle additives, e.g., n-Dy 2 O 3 [10], n-SiO 2 [11], n-carbon [2,4], n-tubes of carbon [3] and n-diamond [5], the best performance yet seen, is with nanosized carbon derivatives. In fact it might be interesting to inter-compare the high field critical current (J c ,H) behaviour resulting from carbon, when substituted for boron (MgB 2-x C x ) with that when it (or its derivatives) are introduced as additive.…”