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BYU study another step in the march toward
better superconductors
Salt Lake City, UT, 22
February 2007: At a seminal meeting in 1987, physicists shocked the
scientific community when they reported that certain ceramics can conduct
electricity with no resistance at low temperatures. Since then, scientists have
been dreaming of trains that levitate on magnetic fields, practical electric
cars, hyper-efficient power lines and the other technological marvels that would
be made possible by a material that could similarly “superconduct” electricity,
but at room temperature.
Near the 20-year
anniversary of that scientific symposium, called “the Woodstock of physics” in
contemporary media accounts, a
Brigham Young
University researcher is part of a team that has taken science one step closer
to this “holy grail.”
Branton
Campbell, assistant professor of physics, in collaboration with the
University of Tennessee's
Pengcheng Dai and others, has published a
paper (subscription required) in the high-profile journal
Nature Materials
that explains the behavior of an important class of superconducting
ceramics.
“Whoever finally
succeeds in discovering a room temperature superconductor is going to win a
Nobel Prize -- it’s a no-brainer,” said Campbell. “But until you know how the
atomic structure of a material relates to its properties, you don’t know what to
do to change the properties to make a better superconductor. When you know
what’s bad, you can try to remove it, and when you know what's good, you can try
to add more of it.”
The team took tiny
samples of ceramic crystals to what Campbell calls the most powerful X-ray
machine in the world, a billion-dollar facility located at
Argonne National Laboratory
near Chicago, where he was once a postdoctoral researcher. There they shined a
needle-thin X-ray beam onto the crystals and mapped out the pattern of scattered
X-rays to determine the location and type of each atom in the crystal structure.
They also used a similar technique called neutron powder diffraction.
There are two
principal types of copper-oxide ceramics that usually don’t even conduct
electricity at room temperature, but become superconductors at low temperature.
One type behaves quite differently from the other, which had scientists
wondering if two separate physical mechanisms might be at work. It was a
long-standing mystery why so-called “electron-doped” ceramics cannot
superconduct until after they have been subjected to special high-temperature
chemical treatments.
The team Campbell was
part of showed that the treatments repair previously unreported atomic-scale
defects in the material. Further, once the defects are repaired, the basic
features of the two types of materials are very similar after all, suggesting
that one theory is enough to explain the mechanism of ceramic superconductivity.
“With the theory of
ceramic superconductors in a state of confusion, anything we can do to eliminate
distractions is very helpful,” Campbell said. “We propose that efforts to
synthesize defect-free materials should lead to better superconductors.”
Other researchers who
contributed to the study have affiliations with the National Institute of
Standards and Technology, the University of Maryland, Oak Ridge National
Laboratory, Argonne National Laboratory, and Tokyo’s Central Research Institute
of Electric Power Industry.
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