| Abstract |
| Partially double-filled skutterudites were prepared via encapsulated melting and hot pressing processes. The skutterudite phase was successfully synthesized through partial double filling of La/Yb and substitution of Co. A small quantity of secondary phase (marcasite FeSb2) was formed, but its formation was suppressed by increasing Co charge compensation. The marcasite phase was detected in all specimens, which was because charge compensation was not sufficiently performed owing to the partial filling with low valence ions of La3+ and Yb2+/3+. Hot-pressed specimens showed relative densities higher than 97.4% compared to the theoretical density. The calculated lattice constant ranged from 0.9129 to 0.9142 nm. As the contents of La and Co increased, the lattice constants decreased; thus, the filling and substitution were confirmed. The electrical conductivity decreased and the Seebeck coefficient increased with increasing La filling and Co substitution. The thermal conductivity significantly decreased with increasing Co substitution, and was further slightly lowered with increasing La filling. (La0.75Yb0.25)0.8Fe3CoSb12 yielded a maximum Seebeck coefficient of 168.2 μVK-1 at 823 K, a maximum power factor of 2.67 mWm-1K-2 at 723 K, and the lowest thermal conductivity of 2.09 Wm-1K-1 at 323 K. As a result, (La0.75Yb0.25)0.8Fe3CoSb12 exhibited the highest dimensionless figure of merit, ZT = 0.66 at 823 K.
(Received September 16, 2019; Accepted October 21, 2019) |
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| Key Words |
| thermoelectric, skutterudite, partial double filling, charge compensation |
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