Potential For New Superconducting Material Advances

Scientists in the Applied Superconductivity Center in the College of Engineering at the University of Wisconsin-Madison added oxygen during a processing step for making magnesium-diboride thin films. The resulting alloy can carry 100,000 amps of current per square centimeter in very strong magnetic fields (10 tesla) and withstand twice as high a magnetic field as the current commercially used superconducting material, niobium-titanium.

Results of the study, conducted in collaboration with chemist Robert Cava's research group at the Princeton Materials Institute, are detailed in the Thursday, May 31, issue of the journal Nature.

Previous attempts to improve superconducting properties by alloying magnesium diboride as a bulk material have not been successful, says Chang-Beom Eom, professor of materials science and engineering and lead author of the paper. Thin films, however, are comprised of layers just a few atoms thick.

"We discovered this material can be alloyed in thin film by a different element. At the same time, that can improve substantially one of the very important properties: the critical field," Eom says.

Superconductors must maintain high current densities, yet withstand a high magnetic field, to function in commercial applications such as electrical power transmission lines, motors and superconducting magnets.

Superconducting materials can conduct electricity with almost no loss of energy. Earlier this year, Japanese scientists discovered that magnesium diboride superconducts up to 39 degrees Kelvin (minus 390 degrees Fahrenheit), almost twice the temperature of any other metallic superconductor. Just a short while later, UW-Madison researchers David Larbalestier, Eric Hellstrom, Susan Babcock and Eom overcame another challenge when they found evidence that the material can transport high electrical currents because its grain boundaries do not obstruct current flow.

In addition to solidifying the material's commercial potential, this latest discovery will lay the scientific groundwork for alloying magnesium diboride in bulk, says Eom. "This alloying can be done in the thin-film form with a different root and that can be adapted to bulk processing in many different ways," he says.