Decoupled charge and heat transport in Fe2VAl composite thermoelectrics with topological-insulating grain boundary networks

Fabian Garmroudi (), Illia Serhiienko, Michael Parzer, Sanyukta Ghosh, Pawel Ziolkowski, Gregor Oppitz, Hieu Duy Nguyen, Cédric Bourgès, Yuya Hattori, Alexander Riss, Sebastian Steyrer, Gerda Rogl, Peter Rogl, Erhard Schafler, Naoyuki Kawamoto, Eckhard Müller, Ernst Bauer, Johannes Boor () and Takao Mori ()
Additional contact information
Fabian Garmroudi: TU Wien
Illia Serhiienko: National Institute for Materials Science (NIMS)
Michael Parzer: TU Wien
Sanyukta Ghosh: German Aeropspace Center (DLR)
Pawel Ziolkowski: German Aeropspace Center (DLR)
Gregor Oppitz: German Aeropspace Center (DLR)
Hieu Duy Nguyen: National Institute for Materials Science (NIMS)
Cédric Bourgès: National Institute for Materials Science (NIMS)
Yuya Hattori: National Institute for Materials Science (NIMS)
Alexander Riss: TU Wien
Sebastian Steyrer: TU Wien
Gerda Rogl: University of Vienna
Peter Rogl: University of Vienna
Erhard Schafler: University of Vienna
Naoyuki Kawamoto: National Institute for Materials Science (NIMS)
Eckhard Müller: German Aeropspace Center (DLR)
Ernst Bauer: TU Wien
Johannes Boor: German Aeropspace Center (DLR)
Takao Mori: National Institute for Materials Science (NIMS)

Nature Communications, 2025, vol. 16, issue 1, 1-9

Abstract: Abstract Decoupling charge and heat transport is essential for optimizing thermoelectric materials. Strategies to inhibit lattice-driven heat transport, however, also compromise carrier mobility, limiting the performance of most thermoelectrics, including Fe2VAl Heusler compounds. Here, we demonstrate an innovative approach, which bypasses this tradeoff: via liquid-phase sintering, we incorporate the archetypal topological insulator Bi1−xSbx between Fe2V0.95Ta0.1Al0.95 grains. Structural investigations alongside extensive thermoelectric and magneto-transport measurements reveal distinct modifications in the microstructure, a reduced lattice thermal conductivity and a simultaneously enhanced carrier mobility arising from topologically protected charge transport along the grain boundaries. This yields a huge performance boost, resulting in one of the highest figure of merits among both half- and full-Heusler compounds, z ≈ 1.6 × 10−3 K−1 (zT ≈ 0.5) at 295 K. Our findings highlight the potential of topological-insulating secondary phases to decouple charge and heat transport and call for more advanced theoretical studies of multiphase composites.

Date: 2025
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DOI: 10.1038/s41467-025-57250-6

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