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July 24, 2012

Optimising Magnesium diboride superconductors

Magnesium diboride (MgB2), was discovered to be superconducting material in 2001. It has has the highest transition temperature (it becomes superconducting, 39K) for a conventional superconductor.

MgB2 could become the superconducting material of choice in numerous medium-range magnetic field applications such as magnetic resonance imaging (MRI). European companies already play a dominant role in MRI and the use of low-cost MgB2 could substantially enhance European competitiveness in a large global market.



Doping effects of ZrC and ZrB2 in the powder-in-tube processed MgB2 tapes (2006)

* Doping MgB2 with carbon (e.g. using 10% malic acid) can improve the upper critical field and the maximum current density (also with polyvinyl acetate).

* 5% doping with carbon can raise Hc2 from 16 T to 36 T whilst lowering Tc only from 39 K to 34 K. The maximum critical current (Jc) is reduced, but doping with TiB2 can reduce the decrease. (Doping MgB2 with Ti is patented.)

* The maximum critical current (Jc) in magnetic field is enhanced greatly by doping with ZrB2.

* Even small amounts of doping lead both bands into the type II regime and so no semi-Meissner state may be expected.


EU researchers initiated the Hipermag project to enhance the performance of MgB2 and thus increase commercial applicability and market penetration. Researchers successfully optimised the microstructure of precursor powders, demonstrating enhanced superconducting properties of carbon-doped nanosized precursors and wires (monofilamentary tapes).

They then developed powder processing techniques leading to development of multifilamentary conductors housed in metallic sheaths. The materials provided the enhanced mechanical stability lacking until now.

Researchers also improved current-carrying capabilities, employing a variety of microscopic and spectroscopic techniques to determine the preferred orientation of MgB2 crystallites. Finally, they evaluated the stability of the superconductors in magnetic fields, explaining novel experimental results with theoretical descriptions.

MgB2 is an intriguing superconducting material with numerous potential uses. Limitations to its commercial exploitation were partially overcome via research carried out by the Hipermag consortium. Future applications include medical imaging and renewable energy.

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