New framework provides insights into thermoelectric materials

The atomistic model is optimised for studying phonons within thermoelectric applications.
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New framework provides insights into thermoelectric materials

More efficient thermoelectric materials could be a possibility in the next few years, thanks to a breakthrough in how researchers understand their inner workings.

Thermoelectric materials directly and reversibly convert heat to electrical energy. They are used in a variety of applications, such as energy harvesting, and the cooling of electronic devices.

One area that scientists and industry alike are interested in is efficiency — whether it is possible to design thermoelectric materials such that they convert heat into electricity more efficiently. Such a boost would open up a range of practical applications for the material.

Thermoelectric materials are more efficient in converting heat into electricity if it acts like a thermal insulator, but is a conductor of electricity. This a feature not found in natural materials.

Now, a research group led by Joe Feser, assistant professor in the Department of Mechanical Engineering at the University of Delaware, has come up with a new suite of tools and a new approach to investigate the limits of heat transport, and to execute nanoscale thermal measurement and simulation.

A key mechanism behind the workings of thermoelectric materials is the scattering of heat-carrying vibrations known as phonons. Researchers been studying phonon scattering so that the size, shape and composition of nanoparticles can be optimised for thermoelectric applications.

Traditionally, phonon scattering has been explained using continuum mechanics models, which are efficient, but ignore the fact that matter is made up of atoms. While this approach is accurate enough on longer length scales, it may not be effective in characterising the behaviour of nanometer-length waves — the very waves involved in heat transport.

Other, more traditional techniques such as molecular dynamics are too slow to simulate scattering for every heat-carrying vibration separately, while others have limited scalability, and are thus unable to simulate larger systems.

The new atomistic model is optimised for studying phonons within thermoelectric applications. It is much more efficient because it does not have to calculate the unnecessary physics. Additionally, the researchers embed facts they already know about the solutions, to further reduce the computing load.

The new framework significantly reduces the amount of computational power needed to simulate phonon scattering and greatly increases the maximum size of the systems that can be studied using computers.

Ultimately, the insight provided by the model will allow precise control over the design of new materials at the level of their tiniest constituents, allowing researchers to come up with materials with unique properties pertaining to thermal conductivity, interface conductance, heat capacity and thermoelectric power factor, which will enable the development of new device technologies.