Superconductor breakthrough could power new advances

The breakthrough, which has improved the effectiveness of yttrium barium copper oxide (YBCO) and related superconducting materials, is said to raise the prospect of more powerful and affordable samples that could have benefits in a number of fields. While some materials need to be cooled to -269°C to superconduct, YBCO superconducts at -181°C, which means it can be cooled with liquid nitrogen, rather than liquid helium. "The properties these samples exhibit could, in time, offer huge commercial potential by improving or reducing the weight and size of applications such as energy storage flywheels, magnetic separators, motors and generators," said Professor David Cardwell, pictured, head of the bulk superconductivity group at the University's Department of Engineering. "These devices already use superconductors to varying degrees. With these new bulk processing techniques, we could greatly improve their power and potential." YBCO is processed most easily in the form of a polycrystalline ceramic, but has to be manufactured as a single grain in order to generate large magnetic fields, since boundaries between grains limit the flow of current in the bulk sample. The Cambridge team have developed a technique to manufacture large single grains of bulk superconductors that involves initially heating the material to a temperature of 1000°C, causing it to part melt. In a series of experiments, various elements, such as depleted uranium, were then added to the chemical composition of the superconductor to generate artificial flux pinning sites within the single grain. When the material cooled and reformed, these added materials retained their integrity and formed physical obstacles that direct the motion of magnetic flux lines, enabling larger currents to flow.