Cold neutrons used in hot pursuit of better thermoelectrics

phys.org | 11/15/2018 | Staff
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Thermoelectric devices are highly versatile, with the ability to convert heat into electricity, and electricity into heat. They are small, lightweight, and extremely durable because they have no moving parts, which is why they have been used to power NASA spacecraft on long-term missions, including the Voyager space probes launched in 1977.

Because applying an electrical current to a thermoelectric causes charged particles to diffuse from the material's hot side to their cold side, they are widely used in cooling applications to pull heat out of systems, such as in heat pumps, fiber-optic devices, and car seats—and to control the temperature of battery packs. The process is also reversible and can effectively reclaim "waste heat" to generate useful electricity from hot surfaces, such as a vehicle's tail pipe.

Versatility - Reliability - Technology - Applications - Challenge

Despite their versatility and reliability, using thermoelectric technology in many applications remains a challenge, because of their relatively high cost and inefficiency compared with conventional power and heating or cooling systems. For maximum efficiency, thermoelectrics need to be both good conductors of electricity and poor conductors of heat—properties rarely found in the same material.

Engineers from Duke University are using cold (lower- energy) neutron scattering techniques at Oak Ridge National Laboratory (ORNL) to study the vibrational motions of atoms, called "phonons," which is how heat propagates through thermoelectric materials. By understanding how phonons move and are scattered within thermoelectrics, the scientists hope to eventually control phonon and electron transport to improve electrical conductivity while minimizing heat flow.

Neutrons - Materials - Energies - Energy - Phonons

"We are using neutrons to study thermoelectric materials, because we can tune their energies to match the lower energy of the phonons, which provides a higher resolution," said Tyson Lanigan-Atkins, a Ph.D. student at Duke, in a group working under Olivier Delaire, associate professor of mechanical engineering and materials science. "Neutrons also enable us to conduct research in more...
(Excerpt) Read more at: phys.org
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