News Column


June 1, 2014


Research from North Carolina State University finds that impurities can either hurt or help the performance in a type of superconductive material expected to find use in a host of applications, including future particle colliders. The size of the impurities determines whether they help or hinder the material's performance.

At issue is a superconductive material called bismuth strontium calcium copper oxide (BÍ2212). It is the only high-temperature superconductor that can be made as a round wire, and it is expected to have applications in magnets for use in everything from magnetic resonance imaging technologies to the next generation of supercolliders-almost anything that fails under the category of high-energy physics or requires a very high magnetic field, researchers say.

The researchers found that nanoscale impurities, from 1.2 to 2.5 nanometers wide, appear to improve Bi2212's performance as a superconductor by serving as centers for pinning magnetic flux in place. Without the pinning centers, the magnetic vortices can move, creating resistivity and impeding superconductivity when a magnetic field is present. On the other hand, large-scale impurities, measured in microns, are detrimental to Bi2212's superconductivity because they are large enough to act as barriers to current, forcing electrons to change their paths and weakening the material's superconductivity.

A key next step will be for materials engineers to reassess long-standing processing protocols for BÍ2212 wires to determine how to minimize the formation of the large-scale impurities.

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Source: Signal

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