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Published May 27, 2008 | Supplemental Material
Journal Article Open

Improved Thermoelectric Performance in Yb_(14)Mn_(1−x)Zn_xSb_(11) by the Reduction of Spin-Disorder Scattering


Rare-earth transition metal compounds Yb_(14)Mn_(1−x)Zn_xSb_(11), isostructural with Ca_(14)AlSb_(11), have been prepared using a metal flux growth technique for thermoelectric property measurements (with x = 0.0, 0.2, 0.3, 0.4, 0.7, 0.9, and 1.0). Single-crystal X-ray diffraction and electron microprobe analysis data indicate the successful synthesis of a solid-solution for the Yb_(14)Mn_(1−x)Zn_xSb_(11) structure type for 0< x < 0.4. Hot-pressed polycrystalline samples showed that the product from the flux reaction was a pure phase from x = 0 through x = 0.4 with the presence of a minor secondary phase for compositions x > 0.4. High-temperature (298 K–1275 K) measurements of the Seebeck coefficient, resistivity, and thermal conductivity were performed on hot-pressed, polycrystalline samples. As the concentration of Zn increases in Yb_(14)Mn_(1−x)Zn_xSb_(11), the Seebeck coefficient remains unchanged for 0 ≤ x ≤ 0.7 indicating that the free carrier concentration has remained unchanged. However, as the nonmagnetic Zn^(2+) ions replace the magnetic Mn^(2+) ions, the spin disorder scattering is reduced, lowering the resistivity. Replacing the magnetic Mn^(2+) with non magnetic Zn^(2+) provides an independent means to lower resistivity without deleterious effects to the Seebeck values or thermal conduction. Alloying the Mn site with Zn reduces the lattice thermal conductivity at low temperatures but has negligible impact at high temperatures. The reduction of spin disorder scattering leads to an ∼10% improvement over Yb_(14)MnSb_(11), revealing a maximum thermoelectric figure of merit (zT) of ∼1.1 at 1275 K for Yb_(14)Mn_(0.6)Zn_(0.4)Sb_(11).

Additional Information

© 2008 American Chemical Society. Received 19 December 2007. Published online 24 April 2008. Published in print 1 May 2008. We thank Sarah Roeske for aid with the electron microprobe, James Fettinger, and Håkon Hope for assistance with the single-crystal refinement. Catherine A. Cox was supported by a NSF funded Bridge to Doctorate fellowship. Portions of this work were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This research was funded by NSF DMR-0600742 and NASA/Jet Propulsion Laboratory.

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