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, and a reduced lattice thermal conductivity and enhanced carrier mobility are simultaneously found. This yields a huge performance boost − far beyond the effective-medium limit − and results in one of the highest figure of merits among both half- and full-Heusler compounds, z≈1.6×10−3K−1 (zT≈0.5) at 295 K. Our findings highlight the potential of secondary phases to decouple charge and heat transport and call for more advanced theoretical studies of multiphase composites.
@article{arxiv.2410.07785,
title = {Decoupled charge and heat transport for high-performance Fe$_2$VAl composite thermoelectrics},
author = {Fabian Garmroudi and Illia Serhiienko and Michael Parzer and Sanyukta Ghosh and Pawel Ziolkowski and Gregor Oppitz and Hieu Duy Nguyen and Cédric Bourgès and Yuya Hattori and Alexander Riss and Sebastian Steyrer and Gerda Rogl and Peter Rogl and Erhard Schafler and Naoyuki Kawamoto and Eckhard Müller and Ernst Bauer and Johannes de Boor and Takao Mori},
journal= {arXiv preprint arXiv:2410.07785},
year = {2024}
}