Improved Thermoelectric Performance in Yb14Mn1−xZnxSb11 by the Reduction of Spin-Disorder Scattering

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• 作者：Shawna R. Brown ; Eric S. Toberer ; Teruyuki Ikeda ; Catherine A. Cox ; Franck Gascoin ; Susan M. Kauzlarich ; G. Jeffrey Snyder
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：May 27, 2008
• 年：2008
• 卷：20
• 期：10
• 页码：3412 - 3419
• 全文大小：1229K
• 年卷期：v.20,no.10(May 27, 2008)
• ISSN：1520-5002

文摘

Rare-earth transition metal compounds Yb₁₄Mn_1−xZn_xSb₁₁, isostructural with Ca₁₄AlSb₁₁, 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 Yb₁₄Mn_1−xZn_xSb₁₁ 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&ndash;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 Yb₁₄Mn_1−xZn_xSb₁₁, the Seebeck coefficient remains unchanged for 0 ≤ x ≤ 0.7 indicating that the free carrier concentration has remained unchanged. However, as the nonmagnetic Zn²⁺ ions replace the magnetic Mn²⁺ ions, the spin disorder scattering is reduced, lowering the resistivity. Replacing the magnetic Mn²⁺ with non magnetic Zn²⁺ 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 Yb₁₄MnSb₁₁, revealing a maximum thermoelectric figure of merit (zT) of ~1.1 at 1275 K for Yb₁₄Mn_0.6Zn_0.4Sb₁₁.