A magnetic field of 17.6 Tesla, about 100 times stronger than a conventional fridge magnet, has been trapped in a high-temperature gadolinium barium copper oxide (Gd-Ba-Cu-O) superconductor by engineers at the University of Cambridge. The field breaks the previous record by 0.4 T, a record set by Masato Murakami from the Shibaura Institute of Technology in Japan with a ceramic superconductor, which had stood for more than a decade.
The potential of superconductors lies in a much wider range of technological fields than used to date including next-generation medical imaging, electricity distribution and energy-trapping flywheels, "magnetic separators" for mineral refinement and pollution control and levitating transport systems. Success in these areas will, however, hinge on our better understanding of the behavior of these zero-resistance materials and the development of better materials that work at higher temperatures. Fundamentally, the magnetic field that can be generated within a superconductor correlates with its electrical current capacity.
The best practical superconductors carry a current at an ampage about 100 times greater than copper metal. However, record-breaking magnetic fields are achievable in materials such as Gd-Ba-Cu-O, which have been fabricated as a single grain of material using a melt processing technique. Now, Cambridge's David Cardwell working with collaborators at Boeing and Florida State University have nudged Murakami's record aside with a similar, but subtly different, cuprate material. They used thin sheets of copper oxide with interstitial gadolinium and barium atoms. The previous record holder was based on yttrium, rather than gadolinium.
The disadvantage of attempting to induce a large magnetic field in such brittle ceramics is that the forces involved can shatter the superconductor like a bone china cup smashed on a stone floor. In order to trap the magnetic field, the team modified the microstructure of their Gd-Ba-Cu-O superconductor by creating flux-pinning centers using a melt fabrication process, stacked two disks of the material together and reinforced this with a stainless steel ring to "shrink wrap" the sample on cooling from room temperature to the superconductor's critical temperature. [Durrell et al., Superconductor Sci Technol, (2014) 27, 082001; DOI: 10.1088/0953-2048/27/8/082001]
"This work could herald the arrival of superconductors in real-world applications," enthuses Cardwell. "In order to see bulk superconductors applied for everyday use, we need large grains of superconducting material with the required properties that can be manufactured by relatively standard processes." The team predicts widespread commercialization within five years and the team is developing various applications with its industrial partner Boeing.
David Bradley blogs at the Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".