廃熱をグリーンエネルギーに： 熱電発電機の効率を高めるアプローチ(Waste heat to green energy: Approach boosts thermoelectric generator efficiency)

＜関連情報＞

• https://www.psu.edu/news/earth-and-mineral-sciences/story/waste-heat-green-energy-approach-boosts-thermoelectric-generator
• https://www.cell.com/joule/abstract/S2542-4351(24)00382-9

高エントロピー駆動型ハーフホイスラー合金で熱電性能が向上 High-entropy-driven half-Heusler alloys boost thermoelectric performance

Subrata Ghosh∙ Amin Nozariasbmarz∙ Huiju Lee∙ … ∙ Shashank Priya∙ Wenjie Li∙ Bed Poudel
Joule  Published:September 9, 2024
DOI:https://doi.org/10.1016/j.joule.2024.08.008

Graphical abstract

Context & scale

Thermoelectric (TE) generators offer an eco-friendly energy conversion technology to directly convert heat into electricity through the Seebeck effect, promoting the efficiency of fuel utilization and sustainable energy development. For all types of TE materials, it is crucial and challenging to decouple TE parameters to achieve high power factor (PF) and low thermal conductivity (κ) simultaneously. Most state-of-the-art TE materials excel in either PF or κ. Conventional half-Heusler materials usually introduce “dual-high” (PF and κ), which limits the further enhancement of TE performance. Here, we demonstrated a high-entropy stabilized single-phase half-Heusler alloy, which maintains high PF with a significant low κ, achieving outstanding TE performance in both figure of merit (1.5 at 1,060 K) and TE conversion efficiency (ɳ) of 15% at a ΔT of 671 K. The high-entropy design in half-Heusler materials uniquely displays an effective approach to advancing TE technology.

Highlights

•High-entropy half-Heusler showcases the possibility in achieving high PF and low κ
•MFeSb (M = Nb_0.25Ta_0.25Ti_0.25V_0.25) demonstrates peak zT of 1.5 at 1,160 K
•Single-leg and unicouple modules show ɳ of 15% and 14%, respectively, for a ΔT ∼671K

Summary

High-entropy engineering effectively reduces lattice thermal conductivity (κ_L) in thermoelectric (TE) materials; however, the chemical complexity of multiple elements in high-entropy materials often leads to phase segregation, limiting their electrical transport properties and overall TE performance. Herein, we report a p-type high-entropy stabilized single-phase half-Heusler alloy, MFeSb, specifically designed to enhance configurational entropy by introducing multiple element species on a single atomic site. This material exhibited low κ_L due to phonon group velocity reduction and strong phonon scattering from lattice strain generated through distorted lattices while maintaining a high power factor. The material demonstrated a record high figure of merit (zT) of 1.5 at 1,060 K, with an average zT of ∼0.92 over 300–1,060 K. Furthermore, superior conversion efficiencies of 15% and 14% for a single-leg and a unicouple module at a temperature difference of ΔT ∼671 K were achieved. Our findings provide a new avenue for enhancing TE material performance through high-entropy engineering.