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Liquid-like compound could lead to better thermoelectric devices

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March 26, 2012

In this diagram, the blue spheres represent selenium atoms forming a crystal lattice, whil...

In this diagram, the blue spheres represent selenium atoms forming a crystal lattice, while the orange regions represent the copper atoms that flow through the crystal structure like a liquid (Image: Caltech/Jeff Snyder/Lance Hayashida)

Thermoelectric materials work by converting differences in temperature into electric voltage. If two parts of such a material experience significantly different temperatures, electrons within it will flow from the warmer part to the cooler, creating an electrical current in the process. Using these materials, electricity could be generated by the temperature differences on the inside and outside of jackets, within car engines, or even between the human body and the air around it ... just to list a few examples. An international team of scientists have now discovered that an existing material, which behaves like a liquid but isn't one, displays particularly impressive thermoelectric properties.

The material is actually a solid, consisting of copper and selenium. The selenium takes the form of a rigid crystalline lattice, which the copper atoms easily flow through – it’s described as being similar in principle to a wet sponge, with the copper playing the part of the water.

Because the thermoelectric effect requires there to be a wide temperature gradient, materials that conduct heat are not well-suited to the task – the more a material is able to disperse heat throughout itself, the sooner that material all reaches one uniform temperature. The material should be a good conductor of electricity, however, as the electrons need to be able to move through it with little resistance.

The copper-selenium material meets both criteria. The free and loosely-flowing copper atoms help drive down its thermal conductivity, while the crystal structure of the selenium boosts its electrical conductivity. According to the scientists, its figure of merit (a rating for thermoelectric efficiency) is one of the highest ever recorded for a bulk material.

As long as approximately 40 years ago, the material was being used by NASA to build spacecraft, although its properties were not fully understood at the time.

The research was led by scientists from the Chinese Academy of Science's Shanghai Institute of Ceramics, working with colleagues from the California Institute of Technology (Caltech), Brookhaven National Laboratory, and the University of Michigan. A paper on their findings was recently published in the journal Nature Materials.

Source: Caltech

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
4 Comments

This is a very interesting development. The question, however, is what next? Apart from one or two vague and speculative notions as to what the compound might be capable of, we are told nothing about how this important discovery is likely to affect our lives... and when.

I would have expected a little more 'meat' in this article.

Alien
26th March, 2012 @ 11:22 pm PDT

"The free and loosely-flowing copper atoms help drive down its thermal conductivity, while the crystal structure of the selenium boosts its electrical conductivity."

Is it possible that you mean the inverse? I have trouble following how loosely-flowing copper atoms reduce thermal conductivity, although I could be wrong--my scientific education doesn't extent past highschool.

daedalus
27th March, 2012 @ 06:43 pm PDT

Daedalus, I read the sentence in the article and agree that it seems to be inverted so your high school education was pretty good. I wonder what school Ben went to or if he needs to get a little more sleep. Copper is normally considered to be a good electrical and thermal conductor because it has free electrons. Loosely flowing copper atoms sounds more like a bowl problem.

katgod
1st April, 2012 @ 09:22 am PDT

This might be a little late, but perhaps the way the materials are connected (the selenium has a crystal structure, as stated in the article) matters to a great degree. I'm not sure about the free floating copper though.

DIOMOID
13th June, 2012 @ 02:59 pm PDT
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