Improved Thermoelectric Performance in Yb₁₄Mn_1−xZn_xSb₁₁ by the Reduction of Spin-Disorder Scattering

Abstract

Rare-earth transition metal compounds Yb 14 Mn 1-x Zn x Sb 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 x Sb 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 x Sb 11 , the Seebeck coefficient remains unchanged for 0 e x e 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 .

Magnetic and structural effects of partial Ce substitution in Y b14MnSb11

“…While Ce was only observed on the Yb(2) site for x = 0.32, samples with x = 0.45 and higher show Ce both on the Yb (2) and Yb (4) volume followed by Yb(4), while Yb(1) and Yb(3) have the smallest volumes. 24 Previous work on Eu 13 AMnSb 11 showed that smaller ions such as Ca and Yb prefer to substitute on the Eu(3) and Eu(1) sites while larger ions such as Ba and Sr prefer to substitute on the Eu(2) and Eu(4) sites, 25 respectively, consistent with the Hirshfeld analysis. Since Ce 3+ is similar in size to Yb 2+ , it is surprising that it has such a strong preference for the Yb(2) and Yb (4) Temperature-dependent molar susceptibility data from single crystals with x = 0-0.58 are shown in Figure 3(a) in the temperature range where ferromagnetic ordering is observed.…”

Improved carrier concentration control in Zn-doped Ca5Al2Sb6

“…13 Inspired by our previous investigation of the thermoelectric properties of Zn-doped Yb 14 MnSb 11 , here we consider Ca 5 Al 2Àx Zn x Sb 6 (x ¼ 0, 0.02, 0.05, 0.10, and 0.20). 17 Zn is an attractive dopant due to its low cost and ease of handling. A combination of high temperature transport measurements and classic transport theory is used to compare the effects of Na-and Zn-doping in Ca 5 Al 2 Sb 6 .…”

Thermoelectric properties of the Yb9Mn4.2−xZnxSb9solid solutions

“…5,6 They oen have very low lattice thermal conductivity due to their large unit cells, and it is possible to nely tune their electronic properties by doping, providing a route to improved zT. High thermoelectric efficiency has been demonstrated in a number of different Zintl compounds [7][8][9][10][11][12][13][14][15][16][17] including Yb 14 MnSb 11 (ref. 16 and 18) and YbCd 2Àx Zn x Sb 2 , both of which have zT values above unity at high temperatures.…”