title: Low Sound Velocity Contributing to the High Thermoelectric Performance of Ag8SnSe6.
abstract: Conventional strategies for advancing thermoelectrics by minimizing the lattice thermal conductivity focus on phonon scattering for a short mean free path. Here, a design of slow phonon propagation as an effective approach for high-performance thermoelectrics is shown. Taking Ag8SnSe6as an example, which shows one of the lowest sound velocities among known thermoelectric semiconductors, the lattice thermal conductivity is found to be as low as 0.2 W m-1K-1in the entire temperature range. As a result, a peak thermoelectric figure of meritzT> 1.2 and an averagezTas high as ≈0.8 are achieved in Nb-doped materials, without relying on a high thermoelectric power factor. This work demonstrates not only a guiding principle of low sound velocity for minimal lattice thermal conductivity and therefore highzT, but also argyrodite compounds as promising thermoelectric materials with weak chemical bonds and heavy constituent elements.
authors.affiliation: Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education School of Materials Science and Engineering Tongji University 4800 Caoan Rd Shanghai 201804 China.
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.affiliation: Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education School of Materials Science and Engineering Tongji University 4800 Caoan Rd Shanghai 201804 China.
authors.forename: Siqi
authors.initials: S
authors.lastname: Lin
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Science Beijing 100190 China.
authors.forename: Binghui
authors.initials: B
authors.lastname: Ge
authors.affiliation: Materials Genome Institute Shanghai University Shanghai 200444 China.
authors.forename: Jiong
authors.initials: J
authors.lastname: Yang
authors.affiliation: Materials Genome Institute Shanghai University Shanghai 200444 China.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education School of Materials Science and Engineering Tongji University 4800 Caoan Rd Shanghai 201804 China.
authors.forename: Yanzhong
authors.initials: Y
authors.lastname: Pei
keywords: lattice thermal conductivity; sound velocity; thermoelectric