Thermoelectric materials are essential in the clean energy transition. They generate electricity without heat sources. However, their promise is slowed because most current thermoelectric materials need to produce more power efficiently to be useful for many practical applications.
In the hunt for new, more efficient materials with complex chemical compositions, it has taken a lot of work and experimental testing of each suggested new multi-material composition. Toxic or rare elements have frequently been used in these tests.
Scientists from the University of Houston and Rice University report a novel method to predict the realization of band convergence in a range of materials. They also fabricated a thermoelectric module after proving that one so-designed material—a p-type Zintl compound—would provide extremely effective thermoelectric performance.
They claimed that at a temperature difference of 475 kelvin, or around 855 degrees Fahrenheit, the heat-to-electricity conversion efficiency exceeded 10%.
Zhifeng Ren, director of the Texas Center for Superconductivity at UH (TcSUH) and corresponding author for the paper, said the materials’ performance remained stable for more than two years.
Although several strategies have been employed to increase efficiency, electronic band convergence has drawn interest due to its potential to enhance thermoelectric performance. High performance from thermoelectric materials is typically challenging because not all electronic bands contribute. Creating complex material where all the bands have to work simultaneously to get the best performance is even more difficult.
Because band convergence raises the thermoelectric power factor—which is correlated with the thermoelectric module’s actual output power—it is thought to be a valuable strategy for enhancing thermoelectric materials. However, finding new materials with strong band convergence has taken a long time, and several failed starts have led to this point. Trial and error is the usual method.
Ren said, “Instead of doing a lot of experiments, this method allows us to eliminate unnecessary possibilities that won’t give better results.”
Because band convergence raises the thermoelectric power factor—which is correlated with the thermoelectric module’s actual output power—it is thought to be a useful strategy for enhancing thermoelectric materials. However, finding new materials with strong band convergence has taken a long time, and several failed starts have led to this point.Trial and error is the usual method.
Working:
In a team of ten, the taller members lift the object with the slightest assistance from the shorter ones. In-band convergence, the objective is to increase the similarity between all band members so that everyone can share the burden of carrying the weight. For example, tall band members would be shorter, and short members would be taller.
To ascertain which combinations of the parent compounds may achieve band convergence, the scientists began with four parent compounds containing five elements: ytterbium, calcium, magnesium, zinc, and antimony. After figuring that out, they selected the highest-performing mixture to build the thermoelectric device.
Xin Shi, a UH graduate student in Ren’s group and lead author of the paper, said, “Without this method, you would have to experiment and try all possibilities. There’s no other way you can do that. Now, we do a calculation first, we design a material, and then make it and test it.”
Scientists could also utilize this strategy to develop new thermoelectric materials by applying the computation method to other multi-compound materials. The computation establishes the appropriate parent compound ratios that should be utilized in the finished alloy.
Journal Reference:
Shi, X., Song, S., Gao, G., & Ren, Z. (2024). Global band convergence design for high-performance thermoelectric power generation in Zintls. Science. DOI: 10.1126/science.adn7265
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