Scientists have found a metallic mix that allows superconductivity at higher temperatures than before
THOUGH superconductivity research began with ductile metals -- those capable of being drawn into wires -- 8 years ago, they were sidelined by ceramic concoctions (also known as oxides) of elements like copper, nickel and barium, which could superconduct -- allow the free flow of electricity, without the loss of energy as heat -- at higher temperatures.
Nevertheless, metallic superconductors retain one important advantage: they're less brittle than ceramics and can be fashioned more easily into wires. Recently, these almost forgotten superconductivity candidates got a shot in the arm when scientists at Bombay's Tata Institute of Fundamental Research reported a metallic mix that allowed electrons almost free flow at -260.5oC.
The metal recipe had the following ingredients: nickel, yttrium, boron, and a dash of carbon -- all earlier metallic superconductors were composed of only three elements. The TIFR scientists had early last year reported superconductivity at a lower temperature in a similar mix, but without carbon.
Although these metallic compounds do not pose any immediate threat to the ceramic competitors -- French scientists recently claimed to have achieved superconductivity using ceramics at about -23oC -- they cannot be dismissed out of hand, says R Nagarajan, a member of the TIFR superconductivity group.
The efforts of the TIFR scientists have been internationally acclaimed, but they have also generated some controversy. Though their most recent discovery was accepted by the journal Physical Review Letters and published in January this year, Nagarajan is piqued that credit for the discovery is being given to scientists at a US laboratory -- AT&T Bell Laboratories.
"I don't understand how people could make such a blunder, because our paper was published in Physical Review Letters, dated January 10, 1994, while the Bell Labs work appeared only in the January 13, 1994 issue of the British journal Nature," he explained.
Interestingly, the Bell Labs discovery is being treated as a serendipitous event. According to a report in a recent issue of the International Business Week, the Bell team "finally succeeded late last year, when a technician inadvertently contaminated the compound with carbon".
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