Superconductors again
Every day news about superdrivers comes up. In the previous number (Elhuyar. Science and Technology, vol. 78, December 1993) Under the title “Improving Brands” in the section “Recent Sciences”, we obtained the superconductivity of Zurich at 133 K or -140 ºC. Now, a group of researchers from Houston and another from Grenoble have reached pressure superconductivity at temperatures of 160 K (-133°C) and 150 K (-123°C) respectively.
The material used by both groups is a mixture of copper oxide, barium, calcium and mercury. The Grenoble team consists of scientists from Argentina, Russia and France, while in Houston researchers are led by Mr. Paul Chu.
Superconductivity has been obtained by intense compression of the material at these temperatures. At normal pressure these materials are superconductors at temperatures below 25 K, but in Houston pressures of about 150,000 bars and from Grenoble to about 235,000 bar have affected the samples. The deformation of crystals has allowed to reduce interatomic distances and therefore has increased the critical temperature (when the material becomes superrconductor).
Due to the need for these enormous pressures to become superconductors, it seems that for practical applications these materials will have great difficulties. However, they serve to better understand the phenomenon and will help physicists overcome the recently extended pessimism towards higher temperatures.
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