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Realizing the Promise of Superconductors
| Article
# : |
20517 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
5 / 1992 |
3,087 Words |
| Author
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C. David Chaffee
C. David Chaffee is executive editor of Superconductor Week
and author of The Rewiring of America: The Fiber Optic
Revolution. |
Superconductors. The word in some respects sounds too glittery for science, yet it accurately describes a class of special, almost magical compounds that at low temperatures conduct electrical current without resistance. These materials are being shaped into useful devices and systems that will surely find applications in diverse areas of technology and raise our standard of living.
The world of science was rocked in 1986 and 1987 when a pioneering band of scientists discovered an amazing new group of these exquisite materials that achieved superconductivity at temperatures much higher than any that had been realized in the previous 75 years of superconductivity research. [See "High Temperature Superconductivity," THE WORLD & I, October 1987.] The critical temperature, Tc, the highest temperature at which the material is a superconductor, soared above 77 Kelvins (-196 C or -320 F). While this temperature is unbearable cold to humans, it is the temperature of liquid nitrogen, a cheap and abundant coolant.
The field of superconductivity quickly became split in two, now including both the previously known low temperature superconductors, whose critical temperature is below 25 Kelvin, and the newly discovered high temperature superconductors. The field of low temperature superconductors was a maturing technology in its own right, with effective devices, such as the electromagnets in Magnetic Resonance Imaging (MRI) machines, already in use. However, the development of cost-effective applications for low-temperature superconductors was limited because any devices made from them needed to be cooled by liquid helium, which was relatively expensive (on par with fine scotch) and required bulky containment equipment. In contrast the liquid nitrogen coolant required by the high temperature superconductors, was much less expensive (on par with milk) and required much less bulky containment equipment.
In the 24 moths or so following first discovery of the new class of superconductors by two IBM-Zurich researchers, George Bednorz and K. Alex Mueller, three materials that could superconduct above 77 K were discovered. These included:
Y-Ba-Cu-O (The first to reach such levels, it was discovered by a collaboration between the University of Alabama at Huntsville and the University of Houston. It became known as the yttrium compound, or once its structure was determined, as the 1-2-3 compound.);
Bi-Sr-Ca-Cu-O (Known as the bismuth compound, it was
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