Enhanced critical current density in bulk MgB.sub.2./sub.

0490135 - FZÚ 2019 RIV US eng J - Journal Article
Muralidhar, M. - Higuchi, M. - Kitamoto, K. - Koblischka, M.R. - Jirsa, Miloš - Murakami, M.
Enhanced critical current density in bulk MgB₂.
IEEE Transactions on Applied Superconductivity. Roč. 28, č. 4 (2018), s. 1-5, č. článku 8000405. ISSN 1051-8223. E-ISSN 1558-2515
R&D Projects: GA ČR GB14-36566G
Institutional support: RVO:68378271
Keywords : MgB₂ * X-ray diffraction * critical current density (J(c)) * flux pinning * microstructure
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 1.692, year: 2018

The objectof this investigation is to improve the flux pinning and critical current density (J(c)) of bulk MgB2 materials for daily applications including superconducting permanent magnets. We prepared two sets of bulk MgB2 materials employing commercial high-purity powders of Mg metal and carbon-coated amorphous B using a single-step solid-state reaction process. The first set of samples was produced by a single-step solid-state reaction at various temperatures between 794 degrees C and 806 degrees C in steps of 3 degrees C in pure argon atmosphere to optimize the sintering temperature. Further, the second set of samples was produced from Mg-rich MgB2 material adding 1.5 wt% carbon-coated amorphous B powder to it, combined with 4 wt% of silver. X-ray diffraction analysis showed that samples were single-phase MgB2 with minor trace of impurities. In all samples, sharp superconducting transition temperatures were observed around 38 K, which was decreased around 1 K in MgB2 material produced with 1.5 wt% of carbon encapsulated boron. The critical current densities in Mg-rich MgB2 material with 4 wt% of Ag were lower than in silver-free MgB2 bulks. The sample with 1.5 wt% of carbon-coated B exhibited the highest Jc of 460 kA/cm(2) at 20 K and self-field. Our results demonstrate a strong correlation between the microstructure achieved and the resulting pinning performance.
Permanent Link: http://hdl.handle.net/11104/0284424