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Superconductor clue: just keep it simple.

Many superconductors - materials that put up no resistance to speeding electrons - exist as a result of the trial-and-error tinkering of lab chemists. Hoping for a future of ultra-efficient engines, computers, and other electronics, scientists are forever creating novel superconducting substances. The newest materials have been increasingly complex, but unfortunately their added intricacies haven't yielded big gains in superconductivity at temperatures greater than 125 kelvins.

A report in the March 18 NATURE Suggests it may be time to go back to basics. An international team led by two chemists at Moscow State University in Russia reports it has discovered a new superconductor made with mercury that is refreshingly simple in structure and shows no resistance at temperatures up to 94 kelvins.

The new material, a mercury-barium-copper oxide called mercury-1201, doesn't beat the 125-kelvin record high temperature. But because mercury-1201 contains just a single mercury and copper oxide layer per unit cell of the crystal, it may have certain practical advantages over the champion material, constructed of two thallium and three copper oxide layers.

"The availability of a material with high transition temperature but only a single metal oxide layer may be important for technological applications, as it seems that a smaller spacing between copper oxide planes leads to better superconducting properties in a magnetic field," S.N. Putilin and his colleagues write.

Researchers are eagerly searching for superconductors that can work efficiently when bathed in the magnetic fields generated by engines, magnets, and imaging equipment, says Robert J. Cava of AT&T Bell Laboratories in Murray Hill, N.J. He speculates that magnetic fields may cause fewer disruptive vortices of current in single-layer materials like mercury-1201. "I think we're going to see a little explosion of activity in the chemistry of this particular compound," Cava predicts.

The new material must first prove it can carry high amounts of current in the 94-kelvin temperature range. "Unless it turns out to have some particularly useful property like high capacity to conduct current, I don't think it will get much attention, because it's more difficult to work with, it's still toxic, and it doesn't have a higher transition temperature," comments Art Sleight of Oregon State University in Corvallis.

The promises and pitfalls of mercury-1201 should be unveiled soon, since it can be easily synthesized for study.
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Title Annotation:new mercury-barium copper oxide superconductor is simple in structure
Author:Schmiddt, Karen F.
Publication:Science News
Article Type:Brief Article
Date:Mar 20, 1993
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