High Temperature Thermoelectric Properties of Yb₁₄MnSb₁₁ Prepared from Reaction of MnSb with the Elements

Abstract

Compounds of the Yb 14 MnSb 11 structure type are the highest efficiency bulk p-type materials for high temperature thermoelectric applications, with reported figures of merit (ZTs) as high as ∼1.3 at 1275 K. Further optimization of ZT for this structure type is possible with the development of a simple synthetic route. However, this has been difficult to achieve because of the small amount of Mn required compared with Yb and Sb. A simple synthetic route for Yb 14 MnSb 11 has been developed utilizing a combination of ball milling and annealing to produce phase-pure material followed by spark plasma sintering for consolidation. The materials have been characterized by powder X-ray diffraction before and after spark plasma sintering. The stoichiometric reaction of Yb, Sb, and MnSb provides phase-pure powder by X-ray diffraction. Upon cycling to temperatures greater than 1272 K, Yb 14 MnSb 11 shows the presence of Yb 11 Sb 10 . Additional samples with 5% and 10% excess Mn were also investigated. Adding 5−10% excess Mn does not change the low temperature properties and improves the high temperature ZT, resulting in a ZT of 1.1−1.2 at 1000 K for Yb 14 Mn 1.05 Sb 11 , 30−40% improvement over that of the Sn flux reaction. The increase in ZT is attributed to optimization of the carrier concentration. These results provide a reliable method of bulk synthesis of this Zintl phase and open the way for discovery of new compounds with potential for even higher ZT.

Achieving zT > 1 in Inexpensive Zintl Phase Ca9Zn4+xSb9 by Phase Boundary Mapping

“…Reproducibility of the samples in the three‐phase regions (region 1 and 2) was also confirmed with the Seebeck measurements on the reproduced samples (see Figure S9, Supporting Information). The figure of merit of various state‐of‐the‐art p‐type Zintl phases are shown in Figure a as a function of temperature, illustrating that Ca 9 Zn 4+ x Sb 9 is one of the best p‐type thermoelectric Zintl phases especially in the intermediate temperature region …”

On the Extended Series of Quaternary Zintl Phases Ca13REMnSb11 (RE = La–Nd, Sm, Gd–Dy)

“…Nature solves the electron deficiency in this instance by at least two different mechanisms – employing mixed‐valence of the cations, as demonstrated on the example of Yb 14 ZnSb 11 , or, as our recent studies on Sr 14 Cd 1+ x Sb 11 and Eu 14 Cd 1+ x Sb 11 suggest, these compounds have tendency to incorporate excess Cd/Zn at vacant interstitial sites, thereby augmenting the number of valence electrons. Neither approach, however, brings perfect charge balance (as in the AE 14 MPn 11 phases with M = Al, Ga, In, which are valence precise semiconductors following the Zintl–Klemm formalism), and these compounds are heavily degenerate p ‐type materials or even poor metals , …”

Magnetic remanence in Yb14−RE MnSb11 (RE=Tb, Dy, Ho) single crystals

“…The ferromagnetic ordering is best described as arising from RudermanKittel-Kasuya-Yosida (RKKY) coupling, where the magnetic moments are coupled through the mobile charge carriers [2]. Yb 14 MnSb 11 is also an excellent high temperature p-type thermoelectric material [7,8]. Solid solutions of Yb 14 MnSb 11 have been recently prepared in order to increase the thermoelectric figure of merit of this p-type high temperature material [7].…”