Jun 20, 2008
Superconducting wire gets upgraded
Nanoscale defect engineering is bringing about dramatic improvements in superconducting wire and takes developers a step closer to realizing their dream of ultra-efficient electricity generation and transmission. Amit Goyal and his colleagues at Oak Ridge National Laboratory (ORNL), US, hit the headlines in 2006 when the team incorporated nanodots within a superconducting wire. Now the team has engineered a film with 50% higher critical current density at 65 K and 3 Tesla.
"Our superconducting wire offers excellent performance in high applied magnetic fields," Sung-Hun Wee of ORNL's Materials Science and Technology division told nanotechweb.org. "The result was achieved at higher deposition rates, which gives splayed defects that appear to be more effective in pinning the flux."
Superconductors are materials that lose their electrical resistance when cooled below a certain temperature, but this behaviour can be disrupted by a magnetic field. "When the currents flow in the presence of high applied magnetic fields, there is a Lorentz force imparted on the flux lines, which makes them move," explained Goyal. "The motion of these flux lines causes dissipation and electrical resistance to appear and makes the wire non-superconducting."
The good news is that these magnetic flux lines can be immobilized by introducing columns of three dimensionally, self-assembled barium zirconate (BaZrO3) nanodots into the superconducting structure – something that the group has demonstrated previously.
Grown by pulsed laser deposition, the latest wire consists of a 4 µm thick film of yttrium barium copper oxide that contains 1% (by volume) of BaZrO3. Key to the current work is the introduction of so-called "splayed" nanoscale defects. These extended-column-shaped features are formed at high deposition rates (40 nm/min) and have been shown by the team to provide superior flux-pinning abilities at all field orientations.
Goyal and Wee are keen to get their research out into the market and revealed that the group is working closely with US industry to upgrade commercially available superconducting wires.
The researchers presented their work in Supercond. Sci. Technol..
About the author
James Tyrrell is editor of nanotechweb.org.