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

TLDR: In this article, a solid-solution for the rare earth transition metal compounds Yb_(14)Mn/(1−x)Zn_xSb_(11), isostructural with Ca(14)AlSb/(11), has been prepared using a metal flux growth technique for thermoelectric property measurements.

Abstract: 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 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).