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Researchers say they have increased the amount of current that bulk samples of "high temperature" superconducting materials can carry, a possible step toward making them practical.

In one experiment, a sample of experimental superconductor carried 10 times the amount of current that standard superconducting materials do, the University of Houston said in a statement.Superconductors are materials that carry electricity without resistance. The materials discovered so far must be made very cold to work. Recently, "high-temperature" superconductors have been created that operate at higher temperatures than standard superconductors, which are widely used in medical technology and other areas.

One problem with high-temperature materials is that the amount of electrical current they can carry has been limited.

But University of Houston researchers say that by using special techniques to prepare a sample of superconducting material, they produced high current-carrying capacity at both very low and relatively high temperatures.

For example, at about minus 451 degrees Fahrenheit, the sample carried 20 million amperes per square centimeter of cross-section when exposed to a magnetic field of a certain strength, and 8 million amps per square centimeter in a field 10 times as strong.

That performance is more than 10 times what conventional superconductors can do, the university said.

At minus 321 degrees, the sample carried 1 million amps per square centimeter in the absence of a magnetic field, and 200,000 amps per square centimeter when exposed to a magnetic field.

The research team included C.W. Paul Chu, Pei-Herng Hor and others at the Texas Center for Superconductivity at the university. Their work is scheduled to be published in the journal Modern Physics Letters.

Malcolm Beasley, a professor of applied physics at Stanford University, called the work "a very useful step toward practical use."