Flux pinning properties of B-rich and SiC-doped MgB2 tapes prepared by in situ PIT two-stage heat-treatment process
✍ Scribed by O. Miura; A. Saeki; H. Tomioka; D. Ito; N. Harada
- Publisher
- Elsevier Science
- Year
- 2007
- Tongue
- English
- Weight
- 426 KB
- Volume
- 463-465
- Category
- Article
- ISSN
- 0921-4534
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✦ Synopsis
B-rich and SiC-doped MgB 2 tapes were fabricated by a modified in situ PIT method with two-stage heat-treatment, using Mg flakes with little oxide film. Combination of heat-treatment and rolling process brought about a dense MgB 2 core and a strong inter granular connectivity. For all B-rich MgB 2 tapes T c remained almost 38 K, while T c decreased for SiC-doped MgB 2 tapes. J c for B-rich tapes increased systematically in whole magnetic fields with the increase of B composition ratio. The maximum J c values of 1.8 • 10 5 at 20 K, 0 T and 0.84 • 10 3 A/cm 2 at 3 T were obtained for a specimen with the ratio of Mg:B of 1:2.8. The grain size of B-rich tapes was smaller than that of the stoichiometric one. SiC-doped tapes also achieved J c enhancement mainly in high-fields. Irreversibility fields increased for both MgB 2 tapes. Analyses based on the single vortex pinning theory revealed two factors contributing to the improvement of J c for B-rich tapes. One is an increase of the grain boundary density and the other is an enhancement of the elementary pinning force at grain boundaries. On the other hand, for SiC-doped tapes, such factors slightly increased compared to B-rich tapes. It is believed that this difference of flux pinning behavior originates in the different flux pinning mechanism.