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Room-Temperature Superconductivity? Not Yet
12 December 1996 8:20 pm
Paris--A French newspaper yesterday claimed that scientists here may have discovered a room-temperature superconductor. But in interviews with members of the team that reportedly found this Holy Grail of materials science, ScienceNOW has learned that a bona fide breakthrough is far from certain. "We have no proof at all that the compound is a superconductor," says Alain Mauger of Paris University.
What Mauger and colleagues from the National Institute of Applied Science in Lyon, the Atomic Energy Commission in Paris, and the National Center of Scientific Research in Meudon have found, they say, are magnetic anomalies suggestive of superconductivity in LiBeH3. The compound is one of a family of materials, the lithium-beryllium hydrides, best known as potential rocket fuels.
The researchers found that when the compound is cooled to 298 kelvins, roughly room temperature, its magnetic properties change in a manner that depends on the surrounding magnetic field. The same unusual effect, called magnetic irreversibility, is seen in the familiar copper-oxide-based superconductors at the temperatures where they become superconducting. The French group has also measured a change in the specific heat--the amount of heat stored--in LiBeH3, an effect also seen in copper superconductors at their critical temperatures. The team describes its findings in a paper submitted to the Proceedings of the French Academy of Sciences.
Purdue University theorist Albert Overhauser had predicted about a decade ago that LiBeH3 might be a room-temperature superconductor. However, shortly thereafter, work in Paul Chu's lab at the University of Houston failed to find any traces of superconductivity in this compound.
The French group isn't ready to claim that they've succeeded. For one thing, they haven't measured the electrical resistance of LiBeH3--key to any determination of superconductivity. The news apparently leaked out prematurely when a project grad student defending his thesis dropped hints that the compound might be a room-temperature superconductor in a talk attended by a local reporter for the Lyon Figaro newspaper. The Reuters wire service alerted the rest of the world to the supposed breakthrough. "We are scandalized by the alerting of the press, before our paper is even accepted by our peers," says Mauger. "It was done much too early, and we consider this a grave error." The French Academy of Sciences will meet on Monday to decide whether to release the paper to the press.