Researchers Break Temperature Record on Superconductors

Conventional superconductors can feed electricity with very little resistance and therefore can conduct electricity far more efficiently than ordinary copper. The downside: Superconductors don’t work well unless they’re cooled to extremely low temperatures.

Now a team at the University of Cambridge has broken a decade-old record for containing a magnetic field in a superconductor at a warm – well, relatively warm – temperature. The old record, set by scientists at Japan’s Shibaura Institute of Technology, was to contain a magnetic field with a value of 17.24 Tesla, or about 6,600 pounds of force, in a piece of ceramic smaller than a golf ball.

The Cambridge team outdid that record by 0.4 Tesla. The strength of that magnetic field is roughly 100 times that of a simple kitchen magnet. Their report was published June 27 in the journal Superconductor Science and Technology.

Extreme cold causes the conductor’s atoms to move very little. The more they move, the more they resist conductance of electricity. Conventional superconductors must be cooled close to absolute zero, or -459.67 degrees Fahrenheit, before they superconduct.

Newer superconductors, though, do so at a higher temperatures, above the boiling point of liquid nitrogen (-320.8 degrees Fahrenheit), which makes them relatively easy to cool and therefore less expensive to operate.

Superconductors are used not only in medical devices such as MRI scanners but also are expected to be valuable tools to increase electrical energy efficiency because they can “trap” energy, not leak it as simple copper conductors do.

This works because one byproduct of superconducting is the generation of a magnetic field, and the greater the strength of that field, the more current it can hold and carry. Top-level superconductors now being used often carry currents that are 100 times greater than copper can.

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The Cambridge team’s superconductor was a ball about an inch in diameter made of a substance called gadolinium barium copper oxide, or GdBCO, which can superconduct at higher temperatures. The Japanese team, working in 2003, used a similar but subtly different superconductor.

To contain so much energy, the researchers turned to materials called cuprates, or alternate layers of thin sheets of copper and oxygen that were the first high-temperature superconductors to be discovered. But cuprates in the GdBCO ball can be so brittle that they tend to explode when they’re used to contain huge amounts of energy.

To solve that problem, the Cambridge team made slight modifications to the GdBCO ball, then belted it in stainless steel to hold it together.

That the Japanese record stood for 11 years is a testament to the rigors of such research, according to Professor David Cardwell of Cambridge’s Department of Engineering, who led the research. “The fact that this record has stood for so long shows just how demanding this field really is. … There are real potential gains to be had with even small increases in field.”

By Andy Tully of Oilprice.com