New material could be energy source

PASADENA, Calif., March 22 (UPI) -- U.S. researchers say they've identified a new thermoelectric material that may lead to efficient conversion of heat into electricity and vice versa.

A thermoelectric material generates electricity when there is a temperature difference between one end of the material and the other.

Thermoelectric materials have been used to power spacecraft ranging from Apollo to the Curiosity rover now headed for Mars, but can also be utilized to capitalize on the wasted heat from automobile engines or industrial machinery.

Researchers at the California Institute of Technology have reported a promising new thermoelectric material can be made from copper and selenium, a solid that exhibits liquid-like behaviors due to the way its copper atoms flow through the selenium's crystal lattice.

"It's like a wet sponge," researcher Jeff Snyder said. "If you have a sponge with very fine pores in it, it looks and acts like a solid. But inside, the water molecules are diffusing just as fast as they would if they were a regular liquid.

"That's how I imagine this material works. It has a solid framework of selenium atoms, but the copper atoms are diffusing around as fast as they would in a liquid."

A thermoelectric material must be good at conducting electricity but bad at conducting heat, otherwise heat from the hot end would move to the cool end too fast and the whole material would rapidly reach the same temperature, stopping the flow of electrons.

"That's how I imagine this material works. It has a solid framework of selenium atoms, but the copper atoms are diffusing around as fast as they would in a liquid."

The crystal structure of the selenium helps conduct electricity, while the free-flowing copper atoms behave like a liquid, damping down thermal conductivity, the researchers said.