Magazine article Science News

The Chemistry of Superconductivity

Magazine article Science News

The Chemistry of Superconductivity

Article excerpt

The chemistry of superconductivity

The unprecedented rate of evolution--some would say revolution--in high-temperature superconductivity has catalyzed the physical sciences as few topics have since the World War II effort to harness the atom. In recent weeks, researchers have been abandoning sleep and home life to collaborate across disciplines and among laboratories in an all-out rush to understand why certain new copper oxides lose all electrical resistance at the "high' (above liquid-nitrogen) temperatures of 77 to 90 kelvins and beyond (SN: 3/28/87, p.196).

With only 10 days' planning, researcherspresented a tutorial on the chemistry of these materials at the American Chemical Society's spring meeting in Denver last week. It was an important forum, according to Arthur Sleight of E.I. duPont de Nemours in Wilmington, Del., since the properties of and the production techniques for high-temperature superconducting materials "have largely been discovered through solid-state chemistry.'

Sleight reports finding a new attributeassociated with oxide superconductors. Previously, only one or two electrons were found occupying the essential ingredient's --say niobium's--d-orbital, or outermost subshell of electrons. In the new 90 K materials, where copper appears to be the essential element, there are nine. This suggests a new range of materials that may qualify for substitution, he says--those whose d-orbital is "nearly filled' instead of "nearly empty.'

The first announcement of a 90 Ksuperconductor--the highest-temperature material at which electrical resistance has been demonstrated to cease-- was made by physicist Paul Chu and his colleagues (SN: 3/14/87, p.164). But no sooner had Chu begun circulating preprints on the work than chemists joined the fray. The Chu preprint arrived on a Friday, recalls Edward M. Engler of IBM Almaden Research Center in San Jose, Calif. …

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