Strongly reduced lattice thermal conductivity in Sn-doped rare-earth (M) filled skutterudites M _x Co₄Sb_12-y Sn _y , promoted by Sb-Sn disordering and phase segregation.

ABSTRACT: CoSb₃ thermoelectric skutterudite has been filled with rare-earth metals (M = La, Ce, Yb) and partially doped with Sn in specimens of M _x Co₄Sb_12-y Sn _y stoichiometry. This has been achieved under high-pressure conditions at 3.5 GPa in a piston-cylinder hydrostatic press. A structural investigation using synchrotron X-ray diffraction data reveals a phase segregation in twin skutterudite phases with filling fraction fluctuation and different unit-cell sizes. As a result of three effects acting as phonon scatterers, namely the rattling effect of M at the wide 8a cages of the cubic Im3̄ structure, the phase segregation, and the intrinsic disorder introduced by Sn substitution at the Sb sublattice, the total thermal conductivity (κ) dramatically falls to reach minimum values under 2 W m^-1 K^-1, well below those typically exhibited by other thermoelectric materials based upon single-filled skutterudites. The power factor is substantially enhanced to 1.11 mW m^-1 K^-2 in Yb_0.5Co₄Sb_11.6Sn_0.4 with respect to the unfilled composition, as a result of the charge transfer promoted by the filler.

SUBMITTER: Gainza J 

PROVIDER: S-EPMC9037351 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature