Band convergence calculations unlock high-performance thermoelectric materials

In a recent study published in ScienceResearchers from University of Houston and Rice University found ways to predict band coordination in different materials. They designed the material using a p-type Zintl compound to increase thermoelectric efficiency, resulting in a heat-to-electricity conversion efficiency of more than 10%.

The research team’s home-made energy conversion efficiency measurement device can also measure the temperature of the cold side. Image credit: University of Houston

Because thermoelectric materials can generate power from heat sources that go to waste without generating additional greenhouse emissions or requiring significant upfront investment, they are critical to the clean energy transition. However, most thermoelectric materials on the market today are limited in their potential because they cannot efficiently generate enough power for many real-world applications.

The search for new, more efficient materials with complex chemical compositions requires a lot of work and experimental testing of each proposed new multimaterial composite. Toxic or rare elements are often used in these experiments.

The researchers of this study stated that at a temperature difference of 475 K, or about 855 ºF, the heat-to-electricity conversion efficiency exceeded 10%.

The research’s corresponding author, Zhifeng Ren, is director of the Texas Center for Superconductivity at the University of Houston (TcSUH). He said the commodity’s performance had been steady for nearly two years.

Although many strategies have been used to increase efficiency, electronic band integration has attracted interest due to its ability to improve thermoelectric efficiency.

It is generally difficult to obtain high efficiency from thermoelectric materials because not all electronic bands in a material contribute; It is even more difficult to create a complex object where all the bands work simultaneously to get the best performance.

Jifeng Ren, research associate professor, Texas Center for Superconductivity, University of Houston

The scientists’ initial goal, he said, is to figure out how to create a material where each of the various energy bands can improve overall performance. They showed that the calculation is theoretically and practically accurate, and developed a module to verify the high performance achieved at the device scale.

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Band convergence raises the thermoelectric power factor, which is related to the actual output power of the thermoelectric module. It is considered as a useful strategy to improve thermoelectric materials. However, until now, the search for novel materials that exhibit substantial band cohesion has been difficult and fraught with setbacks.

The standard approach is trial and error, instead of doing a lot of testing, this method allows us to eliminate unnecessary possibilities that don’t produce the best results..

Jifeng Ren, research associate professor, Texas Center for Superconductivity, University of Houston

Paul CW Chu and May B. Ren in Condensed Matter Physics at the University of Houston. He is also the Cern Endowed Chair.

The researchers used a high-entropy Zintl alloy, YbXK1-xMGYZn2-yearSB2, as a case study, the creation of a sequence of bands whereby the bands were all achieved simultaneously. It was conducted to predict how to efficiently create the most useful product.

According to Wren, if ten people try to lift an object, the taller members of the group will bear more of the weight, while the shorter members will not contribute as much. In band coordination, the goal is to increase unity among all band members so that everyone can share the burden of carrying the weight. For example, taller band members tend to be shorter and shorter members tend to be taller.

To find out which combinations of parent compounds could achieve band coordination, the researchers started with four parent compounds containing five elements: ytterbium, calcium, magnesium, zinc, and antimony. After discovering that, they chose a compound with higher efficiency to make a thermoelectric device.

Without this method, you have to experiment and try all the possibilities; You have no other way to do it. Now, we first do a calculation, we design an object, and then we build it and test it.

Xin Shi, student lead author and graduate student, University of Houston

Researchers can use this strategy to develop new thermoelectric materials by applying the computational method to other multi-composite materials. The calculation establishes the appropriate parent mix proportions to be used in the finished mix.

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A researcher at the Texas Superconductivity Center, Dr. Shawei Chang, from the Department of Materials Science and Nanoengineering at Rice, and Dr. Gao is now at the University of Houston.

Journal Note:

Shi, X., and many others. (2024) Global band integration design for high efficiency thermoelectric power generation in Zintls. Science. https://doi.org/10.1126/science.adn7265

Source: https://www.uh.edu/

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