Low Thermal Conductivity and Magneto-suppressed Thermal Transport in a Highly Oriented FeSb₂ Single Crystal

Thermoelectric materials have been widely explored for the potential applications in power generation and refrigeration fields. High thermal conductivity (∼500 W/m K) of single-crystal FeSb₂ limits the application in cryogenic cooling. In this work, the FeSb₂ single crystal has been synthesized by the self-flux method. The rocking curve results reveal that the single crystal possesses quite high crystallinity. The micromorphology image shows that the single crystal is pyknotic without observable pores or cracks. Surprisingly, the thermal conductivity is reduced by 2 orders of magnitude compared with the previous reports, which can be attributed to the enhanced phonon scattering by the defects and impurities. Furthermore, the magnetic field can further suppress the thermal transport by reducing the phonon mean-free path. The maximum suppression rate of the thermal conductivity reaches 14% at 60 K when the magnetic field varies from 0 to 9 T. In this work, we have prepared the FeSb₂ single crystal with low thermal conductivity, and the magneto-suppressed thermal transport strategy can be applied to other thermoelectric materials.