Strong enhancement of In-Field Critical Current Density
at 20K in MgB₂ with Minute Additions of Dy₂O₃ and B₄C

P. Mikheenko^(1,2), S. K. Chen⁽¹⁾, J. L. MacManus-Driscoll⁽¹⁾

(1) Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, e-mail: jld35@cam.ac.uk
(2) Metallurgy and Materials, School of Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

Abstract - Minute additions of a combination of Dy₂O₃ and B₄C have been used to enhance both pinning and upper critical field in MgB₂ to the level suitable for MRI applications at 20 K. A delicate balance of Dy₂O₃ and B₄C additions is required to improve pinning without significantly reducing connectivity between grains. The Dy₂O₃ nanoparticles react with B to form 10-15 nm DyB₄ nanoparticles, while B₄C supplies carbon into MgB₂ crystal lattice and increases the upper critical field. The optimum level of Dy₂O₃ and B₄C additions is ~0.5 wt. % of Dy₂O₃ and 0.04 wt. % of B₄C, yielding a J_c (20K) of 10⁵A.cm^-2 at 2.7 T.

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Manuscript received September 5, 2007; accepted October 15, 2007. Reference No. ST6, Category 2
Published in Appl. Phys. Lett. 91, 202508,2007