Scientists look at less expensive ways to carry electricity. Superconductors don't need as much cold to work efficiently
Boston — Hopes for faster trains, faster computers, and more-efficient ways of producing electricity are rising because of breakthroughs taking place in the field of superconducters. Researchers are rapidly boosting the temperatures at which superconductors operate, with results that are eclipsing those of even a few weeks ago.
Superconductors are materials that when cooled to extremely low temperatures stop resisting the flow of electricity, essentially giving electricity a ``free ride.'' This leads to much more efficient use of electricity, which loses some of its energy as heat when it flows through normal conductors, such as copper wire.
It's the lack of this resistance in superconductors that makes them ideal for such things as electromagnets, high-speed computers, electric transmission lines, electric motors, and even magnetic levitation trains, which hover above the tracks.
Superconductors are most widely used in powerful electromagnets for research ranging from fusion to high-energy particle physics. So far, the only commercial application is in medicine, where superconducting magnets are used to take magnetic ``pictures'' of the human body.
But a major reason that superconductors are not more widely used is because they must be operated at extremely low temperatures. Superconductors need either liquid helium as a coolant, which means working with temperatures of less than 4 kelvins (-452.47 Fahrenheit), or with laboratory refrigeration units that can drop temperatures to about 10 to 12K.
Either way, keeping superconductors cool can be expensive and technically demanding, a major roadblock to wider commercial use.
Now, scientists are making dramatic strides in finding materials and techniques that boost the temperature at which a substance starts to become superconducting. In one case, a team of researchers is set to report that its material completely loses resistance at temperatures near 95K.
To appreciate the progress that figure represents, one need only look at the track record for raising superconductor temperatures. In 1911, Heike Kamerlingh Onnes of the Netherlands discovered the property. He found that mercury became superconducting at 4.2K. By 1973, researchers at Westinghouse Electric Corporation discovered that an alloy of niobium and germanium started to exhibit superconductor characteristics at 23.2K.
Then, last April, scientists at the IBM Zurich Research Laboratory broke through that barrier. Instead of using alloys, they used a ceramic material made up of lanthanum, barium, copper, and oxygen. They reported what looked like the onset of superconductivity at 35K, which ran counter to existing theory.
At the time, ``few believed them,'' says Paul Chu of the University of Houston. Dr. Chu and his colleagues are one of a number of research teams around the world reporting these higher temperatures. But toward the end of last year, experiments in Zurich and at the University of Tokyo confirmed the original Zurich results, and the temperature has been rising ever since.
There are still unknowns in the current crop of materials that researchers are testing. In order to be practical, they must be able to withstand strong magnetic fields and heavy currents. And the material must be able to retain its superconducting properties when worked into a usable form, such as wire or film.