High figure-of-merit in the heavy-fermion UN2 system for radioisotope thermoelectric applications

Abstract

The design of uranium-based thermoelectric materials presents a novel and intriguing strategy for directly converting nuclear heat into electrical power. Using high-level first-principles approach combined with accurate solution of Boltzmann transport equation, we demonstrate that a giant n-type power factor of 13.8 mW/mK^2 and a peak ZT value of 2.2 can be realized in the heavy-fermion UN2 compound at 700 K. Such promising thermoelectric performance arises from the large degeneracy (Nv=14) of heavy conduction band coupled with weak electron-phonon interactions, which is in principle governed by the strong Coulomb correlation among the partially filled U-5f electrons in the face-centered cubic structure. Collectively, our theoretical work suggests that the energetic UN2 is an excellent alternative to efficient radioisotope power conversion, which also uncovers an underexplored area for thermoelectric research.