Researchers at the University of Maryland have reported making a partially superconducting material that is stable at temperatures more than twice as high as the previous mark recorded in the scientific race to use electrical energy more efficiently.
Jeffrey Lynn, a physicist at the College Park campus, said yesterday that he and his colleagues have made a ceramic material that is partly superconducting at a temperature of 260 Kelvin, or about 8 degrees Fahrenheit.
Until now, temperatures in that range have been achieved only briefly, and the effect could not be reproduced readily. The Maryland team has succeeded in making several samples of a material that is stable and easily produced.
It has been known since the turn of the century that some materials can conduct electricity with no resistance near absolute zero, the temperature where molecular motion stops, or about minus 460 degrees Fahrenheit.
In the past 18 months, researchers have discovered superconducting materials that need not be cooled to such low temperatures, but can operate at temperatures of 95 Kelvin, or about minus 288 Fahrenheit.
If superconductors could be made to work at at room temperature or temperatures easily achieved by commercial refrigeration, virtually all uses of electricity would be changed. Electric motors could be made many times more powerful while consuming less energy, and power generation, transmission and storage could be made extremely efficient and considerably cheaper.
In recent months, numerous researchers around the country have reported observing fleeting superconductivity at temperatures of 270 Kelvin, about 27 degrees Fahrenheit. But the scientists have been unable to make the materials behave in the same way twice.
Researchers believe that only a small portion of the materials they have worked with are superconducting, and the rest remain at least partly resistant. They have been working steadily to isolate those small pockets of superconducting material.
The Maryland lab has a similar composite material, with only a few percent that is superconducting, and the effects have not disappeared.
Lynn said this advance puts researchers in a situation like the one that led researchers to the sudden jump up to 95 Kelvin this year. There had been numerous hints of superconductivity at that temperature, but researchers had to try hundreds of chemical mixtures before finding one that was a stable superconductor at that level.
Lynn's mixture is made of powders of yttrium, barium, strontium and copper oxide that are baked in an oxygen atmosphere. Lynn said the material is similar to those that are superconducting at 95 Kelvin, but the baking recipe is somewhat different.
To achieve a fully superconducting material at 250 to 270 Kelvin, Lynn said, some researchers are trying to isolate and study the small portions of superconducting material in a sample. He said his lab will continue with the older approach, that is, simply trying more mixtures and cooking processes, then testing them for the effects of superconductivity.