The effects of Yb11Sb10 and Yb10MnSb9 secondary phases on the high performing thermoelectric material Yb14MnSb11

Abstract

The Yb₁₁Sb₁₀ Zintl phase has long been reported to be a negative secondary phase in the high performing Yb₁₄MSb₁₁ (M = Mn, Mg, Zn) (14-1-11) thermoelectric material. However there have been discrepancies in the literature regarding the effect of this Yb₁₁Sb₁₀ phase on the thermoelectric performance of 14-1-11 compounds. The recent discovery of Yb₁₀MnSb₉ is used here to explain these inconsistencies. Yb₁₁Sb₁₀ and Yb₁₀MnSb₉ are very close materials stoichiometrically and crystallographically. However, despite these similarities, these materials exhibit very different transport properties and thus should have differing impacts on the overall thermoelectric performance of 14-1-11. In this work, we consider how these two phases affect the thermoelectric performance of Yb₁₄MnSb₁₁ when present as secondary phases both through an experimental investigation and an effective medium theory model. Secondary phases in thermoelectrics are often regarded as a consistently negative effect and yet here we show that while the presence of Yb₁₁Sb₁₀ in Yb₁₄MnSb₁₁ reduces the thermoelectric performance, the presence of Yb₁₀MnSb₉, even in large amounts does not dramatically reduce the thermoelectric performance and is shown here to even improve performance. This work provides a deeper understanding of previous works regarding 14-1-11 materials and Yb–Mn–Sb phases and paves the way towards practical application.