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

Author(s)

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 de Boor, Takao Mori

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 Bi_1−xSb_x between Fe₂V_0.95Ta_0.1Al_0.95 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.

Organisation(s)

Department of Materials Chemistry, Dynamics of Condensed Systems

External organisation(s)

Technische Universität Wien, National Institute for Materials Science, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Justus-Liebig-Universität Gießen (JLU), Universität Duisburg-Essen, University of Tsukuba

Journal

Nature Communications

Volume

16

ISSN

2041-1723

DOI

https://doi.org/10.1038/s41467-025-57250-6

Publication date

12-2025

Peer reviewed

Yes

Austrian Fields of Science 2012

104017 Physical chemistry, 103006 Chemical physics, 205019 Material sciences

ASJC Scopus subject areas

General Chemistry, General Biochemistry,Genetics and Molecular Biology, General Physics and Astronomy

Portal url

https://ucrisportal.univie.ac.at/en/publications/a8f7749b-43e6-4b91-8804-77a3630d7f80