TECHNOLOGY

Superconductors heat up

MALCOLM GRAY April 6 1987
TECHNOLOGY

Superconductors heat up

MALCOLM GRAY April 6 1987

Superconductors heat up

TECHNOLOGY

In scores of laboratories around the world, researchers are pursuing one of science’s most elusive goals—to create an everyday material with the near-magical ability to carry electricity without any loss of energy. Since 1911, physicists have known that metals cooled almost to absolute zero, or -273.2°C, lose all resistance to electricity. But because scientists could only produce that phenomenon—known as superconductivity—at extremely low temperatures, the discovery has had limited practical value. Still, during the past 15 months a series of dramatic discoveries has allowed scientists to raise the temperature threshold of superconductivity. And C.W. Paul Chu, a University of Houston physicist, said that he believes scientists will be able to make a superconductor that could function at room temperature.

Researchers say that such an achievement would spark a technological revolution rivalling the 1948 invention by two U.S. scientists of the transistor. Certainly, so-called roomtemperature superconductors would make computer operations speedier and more efficient and permit longdistance electricity transmission without energy loss. In addition, some of the new substances—ceramic compounds containing copper and such less-common elements as barium and yttrium—can also sustain large magnetic fields. As a result, scientists say, superconductors now being developed will improve magnet technology used in equipment ranging from electric generators to medical imaging devices. But researchers stress that they still have obstacles to overcome before superconductors move from the laboratory to everyday use. For one thing, scientists say that they do not yet know if the new materials can carry large amounts of electrical current.

The breakthrough to higher-temperature superconductivity occurred after three years of experiments by Zurichbased scientists Alex Midler and Georg Bednorz. Unlike most of their colleagues, who were investigating metal alloys, the two researchers for the giant computer company IBM Corp. were studying the effects of chilling oxides— substances which normally are poor conductors of electricity. And on Jan. 27, 1986, they mixed a new compound—and saw it lose resistance to electricity at a temperature that was 30°C above absolute zero.

Scientists are still searching for a theory to explain a phenomenon that allows electrons to move freely between the atoms of the transmitting substance. Declared Alex Zettl, a physicist at the University of California at Berkeley: “It’s one of the greatest achievements of theoretical physics, but right now the experimentalists are way ahead of the theory.” Meanwhile, the September, 1986, publication of the Swiss researchers’ work and the widespread availability of the materials used to make the new ceramic compounds has stimulated research. Indeed, superconductor discoveries are proliferating so rapidly that the New York City-based American Physical Society (APS) held a special conference two weeks ago simply to discuss the latest news. The result: 3,000 researchers from around the world flocked to the meeting. Declared physicist and APS fellow Neil Ashcroft: “What we are seeing here is one of the

most exciting developments in decades. It is utterly remarkable, and I think there’s more to come.”

To that end, Canadian scientists contributed to one of the most significant recent advances—helping to formulate a ceramic superconductor that also maintains a powerful magnetic field at -182°C. Ross McKinnon, a physicist on leave from Ottawa’s National Research Council (NRC), was a member of the Bell Communications Research team in Red Bank, N.J., that prepared the compound. And last month NRC crystallographer Yvon Le Page identified the molecular makeup of the experimental compound—a crucial step that allowed researchers to duplicate the formula.

Until that discovery, researchers had to use expensive liquid helium before superconducting materials began working at -250°C. But at -182°C they can use cheaper liquid nitrogen as the cooling agent. For one thing, that switch will lower the costs of sophisticated medical imaging devices. Those scanning machines rely on magnetic fields created by superconductors to detect cancer cells in the body’s natural electromagnetic signals. Declared Le Page: “With the magnets that will become available in a matter of months based on this material, the price will go from millions of dollars to a fraction of a million.” Clearly, that is only a small part of the benefits expected as superconductors come in from the cold.

MALCOLM GRAY

with

WILLIAM LOWTHER

in Washington