Abstract
CoSb3 thermoelectric skutterudite has been filled with rare-earth metals (M = La, Ce, Yb) and partially doped with Sn in specimens of MxCo4Sb12−ySny 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 Yb0.5Co4Sb11.6Sn0.4 with respect to the unfilled composition, as a result of the charge transfer promoted by the filler.
Highlights
With the world facing an unstoppable growth in energy needs, the interest in alternative energy sources becomes greater every day
Many guest atoms,[10,11,12] such as rare-earths,[13,14,15,16] can be incorporated into the structural voids between the octahedra, in materials of MxCo4Sb12 stoichiometry (M 1⁄4 ller element, with x 1⁄4 1 corresponding to complete site- lling, x z 0.5 seems to be the practical limit17,18), tuning the carrier density and reducing the intrinsically high lattice thermal conductivity, which is the main drawback in the thermoelectric performance of the un lled skutterudite
High-pressure synthesis conditions were essential to stabilize the skutterudite materials in short periods of time
Summary
With the world facing an unstoppable growth in energy needs, the interest in alternative energy sources becomes greater every day. Thermoelectric materials, with the ability to convert heat into electricity, can be a good choice to help overcome this problem. The efficiency of these materials can be evaluated with the dimensionless gure of merit,[1,2] ZT 1⁄4 S2T/rkt, where S, T, r and kt are the Seebeck coefficient, absolute temperature, electrical resistivity and total thermal conductivity, respectively. This total thermal conductivity is the sum of the electronic and lattice contributions. The Wiedemann–Franz law connects the electrical conductivity and the electronic thermal conductivity, so a drastic reduction in the lattice thermal conductivity is a key requirement to develop successful thermoelectrics.[19]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
