ICT2014 Abstracts

Yb₁₄MnSb₁₁ is one of the highest efficiency bulk p-type materials for high temperature applications, with a ZT ~1 at 1200 K.  While advances have been made in doping the material to improve properties, the commonly used Sn flux synthesis is not ideal for producing materials on the scale required for making a thermoelectric device.  Preparing a phase pure material by a traditional high temperature stoichiometric reaction of the elements is difficult when one component is present in small quantities, such as Mn in Yb­₁₄MnSb₁₁. Traditional high temperature synthesis techniques for ternary or more complex phase are limited to compounds that are thermodynamically more stable than any mixture of binaries, because in an all solid reaction, solid-solid diffusion rates control the reaction products. A metallurgical approach to the synthesis of Yb­₁₄MnSb₁₁ has been developed by our research group utilizing a combination of ball milling and annealing to produce the material and spark plasma sintering to consolidate it. While this synthesis is able to avoid the common pitfalls of flux synthesis, such as residual flux and low scalability, making a phase pure pellet with the new method is not a trivial matter. We have explored various procedures and precursors in order to expand the chemistry of Yb₁₄MnSb₁₁. This presentation will present the development of this synthetic process and the resulting thermoelectric properties.