A New Critical Temperature High for Calcium-Doped YBCO Superconductor

From NextBigFuture.com

For years superconductor research has focused on improving the performance of YBCO, the most widely used industrial superconductor.

Doping YBCO with calcium can improve its current-carrying capability across grain boundaries by as much as 35 percent – but at a sacrifice. Doping lowers its 91K Tc (critical temperature) to a level uncomfortably close to that of the 77K liquid nitrogen coolant.

To date there have been just two variants of YBCO discovered that will accommodate calcium without Tc loss: Y2CaBa4Cu7O16+ (Tc ~96K) and Y3CaBa4Cu8O18+ (Tc ~99K). Superconductors.ORG today reports a third calcium-doped YBCO formulation has been found that produces a Tc considerably higher than even those two compounds. YCaBa3Cu5O11+ displays a resistive Tc near 107K.

In addition to a resistive Tc near 107K, the R-T plot at page top also shows a rogue phase near 135K. This was likely produced by a 3423C structure that formed as a minority phase. This conclusion was reached by examining the results achieved with a 177K YBCO variant in March 2009. The 3423C has one more barium atom and one more copper atom in the upper part of the structure, further increasing planar weight disparity.

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