Rearranging oxygen for superconductivity.Rearranging oxygen for superconductivity superconductivity, abnormally high electrical conductivity of certain substances. The phenomenon was discovered in 1911 by Kamerlingh Onnes, who found that the resistance of mercury dropped suddenly to zero at a temperature of about 4.2°K;. The superconducting ceramic yttrium-barium-copper oxide behaves like an oxygen sponge, readily sopping sop·ping adj. Thoroughly soaked; drenched. adv. Extremely; very: sopping wet. sopping Adjective completely soaked; wet through Also: ( up or releasing oxygen atoms. A team of researchers has taken a close, careful look at how oxygen content and arrangement influence the temperature at which a material starts to lose its resistance to electrical current. The findings, reported in the Aug. 24 NATURE, overturn certain commonly held views about the effect of oxygen arrangements on the superconducting transition temperature. Researchers often refer to yttrium-barium-copper oxide as the 1-2-3 compound because those numbers represent the relative number of yttrium yttrium (ĭt`rēəm) [for Ytterby, a town in Sweden], metallic chemical element; symbol Y; at. no. 39; at. wt. 88.9059; m.p. about 1,522°C;; b.p. 3,338°C;; sp. gr. about 4.45; valence +3. Yttrium is a highly crystalline iron-gray metal. , barium and copper atoms in the material. Its corresponding oxygen proportion can vary from 6.4 to 7. For certain ranges of oxygen content, its superconducting transition temperature stays relatively constant: about 90 kelvins (-183 [degrees] C) for the range from 6.8 to 7, and 60 kelvins between 6.6 and 6.7. When plotted on a graph of transition temperature versus oxygen content, those regions where the graph levels off appear as plateaus. Many scientists assume these two plateaus correspond to two different arrangements of oxygen atoms within the ceramic. To check this idea, Robert B. Beyers of the IBM (International Business Machines Corporation, Armonk, NY, www.ibm.com) The world's largest computer company. IBM's product lines include the S/390 mainframes (zSeries), AS/400 midrange business systems (iSeries), RS/6000 workstations and servers (pSeries), Intel-based servers (xSeries) Almaden Research Center The IBM Almaden Research Center, located near San Jose, California, is one of IBM's largest research centers, specializing in both basic research in material science and applied research in computer storage, where many refinements and improvements were made in hard disc drive in San Jose San Jose, city, United States San Jose (sănəzā`, săn hōzā`), city (1990 pop. 782,248), seat of Santa Clara co., W central Calif.; founded 1777, inc. 1850. , Calif., and his colleagues developed a special apparatus allowing them to control exactly how much oxygen gets into their samples. They used electron diffraction Electron diffraction The phenomenon associated with interference processes that occur when electrons are scattered by atoms to form diffraction patterns. techniques to study the crystal structures of the resulting materials. "We see a progression of ordered structures," Beyers says. "The only places where we see more than one type of electron diffraction pattern are right in the middle of the plateaus." That's the opposite of what many researchers had expected. EAch plateau seems to represent not a single phase, or type of crystalline arrangement, but a mixture of two phases differing only slightly in oxygen content. At the same time, the researchers find no evidence for mixtures of phases that have very different oxygen contents. "This is the kind of scientific underpinning you need for the development of any consistent, reproducible technology," says Robert A. Huggins of Stanford University. "The oxygen [content] is a critical feature of the properties of these materials. It may even turn out to be what determines who ends up getting the basic patents on the 1-2-3 compounds." |
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