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New Superconductor Hailed As Most Important Recent Advance in Field

February 16, 1988

BOSTON (AP) _ Japanese researchers have discovered a new superconductor that works at higher temperatures, may be easier to develop for practical applications and will make it easier to explain how such materials operate, scientists say.

The new material raises the temperature at which superconductivity occurs to about 243 degrees below zero, a jump of more than 50 degrees above levels attained with previous superconductors, a panel of scientists said Monday at the annual meeting of the American Association for the Advancement of Science.

During the past year, scattered reports have appeared of superconductivity occurring at room temperature or even higher temperatures, but those observations have not been confirmed and are not widely accepted.

In contrast, the properties of the new material were confirmed within days after its discovery was disclosed on Jan. 22 in a newspaper in Japan, the researchers said.

The mixture of bismuth, strontium, calcium, copper and oxygen is not merely a refinement of either of the two known high temperature superconductors, but an entirely new compound that in some respects may exceed the others’ performance, the researchers said.

″I personally am quite happy we have found a third one,″ said K. Alex Mueller of International Business Machines Corp. in Zurich. He won a Nobel Prize last fall for his discovery in January 1986 of the first of the new high-temperature superconductors.

Mueller’s superconductor was made of lanthanum, strontium, copper and oxygen.

Superconductors carry electricity with no resistance and therefore no wasteful dissipation of electricity. Before Mueller’s discovery, superconductivity occurred only at temperatures a few degrees above absolute zero, about 459 degrees below zero. Comparatively expensive liquid helium was required to cool them to the temperatures at which they became superconducting.

A year after Mueller’s discovery, Paul Chu of the University of Houston and others discovered a second superconducting compound made of yttrium, barium, copper and oxygen that became a superconductor above the temperature of liquid nitrogen, 321 degrees below zero. That was important because liquid nitrogen is relatively inexpensive and widely available.

Later in the year, researchers demonstrated that the second compound could carry significant amounts of electrical current, an important requirement for practical application of superconductors.

Last month, a Japanese team led by Hiroshi Maeda discovered the new bismuth superconductor. Maeda did not attend Monday’s meeting.

The new superconductor appears to be flexible, suggesting that it might lend itself more easily than the others to the fabrication of wire, said Angelica Stacey, a chemist at the University of California, Berkeley.

Because the superconductor operates at significantly higher temperatures, its electrical properties at the temperature of liquid nitrogen may be superior to the properties of the other superconductors, said John Rowell of Bell Communications Research in Red Bank, N.J.

As a general rule, the properties of superconductors improve the farther you go below the so-called transition temperature at which they become superconducting, he explained.

Another potential advantage of the new material is that bismuth is more stable than barium, which means that the new superconductor might be less likely to break down chemically over a period of time, said Stacey.

Although the researchers were optimistic that the new compound would have useful properties, they said not enough time had yet elapsed for those properties to be measured.

Philip W. Anderson, a professor of physics at Princeton University in New Jersey, said the availability of a third superconductor will make it easier for researchers to develop theories explaining how high-temperatu re superconductors work.

Anderson said he believes the new superconductors are profoundly different from conventional superconductors.

″What we’ve discovered is not just a new kind of superconductor,″ he said, ″but a new kind of metal.″