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Getting the creeps out of superconductors.

Getting the creeps out of superconductors

Researchers still don't know just how a certain class of ceramic superconductors can carry electricity resistance-free at far less frigid temperatures than any previously discovered superconductors. Nonetheless, materials scientists continue to chip away at fabrication problems that threaten to keep these remarkable ceramics from becoming useful in some potentially far-reaching items--such as superconducting electrical power lines -- featured on many a technological wish list.

R. Bruce van Dover and E. Michael Gyorgy of AT&T Bell Laboratories in Murray Hill, N.J., separately report bombarding thin films of an yttrium-barium-copper-oxide superconductor with neutrons and protons, respectively. The micro-flack generates imperfections in the ceramic, which researchers know are necessary to counter the so-called flux-creep problem. Without a good distribution of the imperfections, lines of magnetic energy tend to creep around in a superconductor's crystal lattice, impeding electrical current.

Bombarding nearly perfect single crystals of the oxide in this way enables them to carry up to 100 times more current than untreated crystals, van Dover and Gyorgy say. Leonardo Civale of IBM's Thomas J. Watson Research Center in Yorktown Heights, N.Y., reports similar results using proton bombardment.

Other AT&T researchers, led by Sungho Jin, report another way of getting the defects into small grains of the same material. Using a sequence of heating and cooling steps to convert a precursor ceramic into the oxide, Jin's team obtains micron-sized grains that carry about 10 times more current than similar grains made by other methods.
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Author:Amato, Ivan
Publication:Science News
Date:Dec 9, 1989
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