Physicists Defy Weakest Link

The newly discovered superconducting material magnesium borate has properties that will have important implications for use as a conductor and a high field-generating device.

Work by Cambridge University's Dr David Cardwell and his colleagues has revealed that the complex material which behaves like ceramics has qualities that overcome problems many superconductors have - it is not particularly sensitive to the application of a magnetic field.

"This is a major breakthrough in this field with exciting implications for potential applications as both a conductor and a high field-generating device," said Dr Cardwell.

Until the late 1980s, theory suggested that superconductors could not exist above minus 240°C (about 30 K).

But a generation of so-called high-temperature superconductors was discovered in 1987 that was developed to superconduct at minus 107°C (166 K).

The higher the electrical currents that a superconductor can carry at a given temperature, the greater its potential for use in everyday life.

Superconductors are used for a variety of applications including magnetic resonance imaging and energy storage devices that provide a steady power supply for underground and overland trains.

Many of the high-temperature superconductors have serious drawbacks. The complex metal oxides are both granular and brittle.

When made into wires or other useful materials, it becomes difficult to pass current from one grain to the next.

These grain boundaries are effectively the weak links to the flow of electricity, severely limiting the application potential of the materials.

Borate reveals that grain boundaries do not form weak links to the flow of current.

The material also overcomes another problem in so much as it appears insensitive to the application of a magnetic field.