Study On The MgB₂ Wires And Tapes Fbricated By The Powder In Tube Method

MgB2 has the highest critical temperature of 39K among non-ceramic superconducting materials. It has weak-link free grain boundaries and is a kind of low cost material,.which could be used under 20K~30K. However, MgB2 reveals a poor Jc property in high magnetic field. Currently in the research of the MgB2 wires and tapes many efforts have been made to improve its grain connection or enhance the Jc dependence on the magnetic field using the method of chemical doping.In this work, un-doped and nano SiC doped MgB2/Fe tapes and wires were fabricated by the Powder In Tube (PIT) technique, and the short samples were synthesized through two different routes of the traditional vacuum sintering and the sparking plasma sintering (SPS). The sintering parameters were optimized in both sintering methods. The X-ray diffraction, scanning electronic microscope and the SQUID were used to characterize the properties of the MgB2 core in MgB2/Fe tapes and wires. The effect of the proportion of Mg, B and SiC as well as the sintering parameters on the phase formation, microstructure and the critical current densities of MgB2/Fe tapes and wires was discussed in details.The results showed that the high purity of MgB2 core could be synthesized by both the traditional vacuum sintering and the sparking plasma sintering and the vacuum sintering environment restrained the oxidation of Mg effectively. Compared to the traditional sintering way, the uniform and good grain connectivity was observed in the MgB2 core with fine gain sizes obtained by SPS during a short period of sintering, which contributed to the good transport properties of the MgB2/Fe tape. The Jc value of the sample sintered by SPS was rather larger than that of the sample sintered by the traditional method. The highest Jc of 8.64×105A/cm2 at 10K, 0T was obtained in the un-doped MgB2/Fe tape sintered at 800℃for 15 minutes by SPS. It is worthwhile to note that the Jc value was decreased much slowly in this sample with the increase of the testing temperature and magnetic field. For example, the Jc was 5.97×105A/cm2 at 20K, 0T, and at 20K, 3T the Jc value was...