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The 1987 discovery of materials that conduct electricity perfectly at temperatures above the boiling point of nitrogen (-196 degrees Celsius) seemed to herald a revolutionary era of technology. But turning the promise of these so-called high-temperature superconductors into commercial reality has proved to be a long, arduous task. It is one thing to produce a small sample of a superconductor for experiments in a laboratory and quite another to manufacture hundreds of meters of high-quality wire for applications. Until recently, the leading commercial high-temperature superconductor technology involved wires made of the elements bismuth, strontium, calcium, copper and oxygen (BSCCO). Now a second generation of wires, composed of yttrium, barium, copper and oxygen (YBCO), looks set to dominate the marketplace.
BSCCO wires are typically made by putting a powder inside a tube of silver that is then heated and drawn out. But that technique has two significant downsides. First, the cost of the silver makes the wires expensive. Second, manufacturers have little ability to control the detailed structure of the BSCCO cores to optimize the superconductor's performance.