High-Temperature Superconductor Developed
A new superconductor that works at relatively high temperatures can carry about 100 times more electricity than earlier versions, an important step toward practical use of these materials, researchers said Tuesday.
The researchers said their discovery appears to provide major clues toward solving a problem that has stumped experts trying to fashion superconductors that can work at relatively warm temperatures to transmit large amounts of power without resistance or loss.
Sungho Jin and colleagues from AT&T; Bell Laboratories in Murray Hill, N.J., found a new way to manufacture superconductors that changes the shape of the microscopic crystals that make up the materials.
Jin said that in its present form, his superconductor might be used for some limited applications, such as small motors. But the importance of the work is the direction it provides for creating even better superconductors.
“We are on the edge now of practical things,” said Robert Dynes, director of chemical physics research at Bell Labs. “We were way off scale before. I hope this will show the way for people to improve it rapidly.”
Brian Maple of UC San Diego agreed that the development appears to be a major improvement.
“This isn’t the ultimate answer, because they are still much lower (in power levels) than what you would want in a lot of applications, but it might be close for certain restricted applications,” Maple said. “It could be a very important step in the right direction.”
Race Started in 1986
Jin plans to present his results today at a meeting in Boston of the Materials Research Society.
Finding materials that are superconducting at room temperature or above is a major goal, because it will allow them to be used without requiring coolants. Superconductors that have been used for many years need extremely cold temperatures to transmit electricity effectively without resistance.
The race to develop high-temperature superconductors began in January, 1986. Johannes Bednorz and Karl Mueller of IBM discovered that copper oxide ceramics could conduct current without resistance at higher temperatures than had been seen before. In October, they were won the Nobel Prize in physics for their work.
A variety of exotic applications of the work have been proposed, including highly efficient power lines and magnetic trains riding on a cushion of air. But practical problems have stood in the way of such uses of superconductivity.
Many new superconductors work at minus 321 degrees Fahrenheit. This is the temperature of liquid nitrogen, a cheap coolant that could be used to hold down the temperature of the superconductors. However, they typically lose their superconducting powers if subjected to large amounts of current or magnetic fields.
At minus 321 degrees Fahrenheit and in a magnetic field of 10 kilogauss--roughly 30,000 times the intensity of Earth’s magnetic field--Bell Lab’s superconductor achieves a current density of 1,000 amperes per square centimeter. Jin said this is 100 to 1,000 times higher than previous materials.
Jin said he created the material by melting a superconducting ceramic and then letting it solidify. This changed the way the crystals that make up the ceramic fit together. Instead of being packed together like grains of sand, the crystals became needle-shaped and lined up in roughly the same direction.
He said this new form greatly reduced resistance barriers that had existed between the sand-like crystals of earlier materials. The material can be formed into wires and other useful shapes.
“We still have to go a long way, but the point we are making here is that we are out of the woods,” Jin said.
Jin’s and Erbil’s reports are among a variety of superconductivity papers being released at the Boston meeting. At the same gathering a year ago, other researchers made some of the first public disclosures of superconductivity that touched off a research scramble around the country.
