ICT2014 Abstracts

In order to prepare an efficient thermoelectric power generator that operates at high temperatures (1200 K), it is necessary to improve the efficiency of the p-type semiconductor leg. One candidate for the highest temperature p-type material is Yb₁₄MnSb₁₁. It is a unique, highly doped p-type semiconductor with a zT ~ 0.8 at 1200 K, when measured heat capacity is used to determine thermal conductivity. It is also an interesting semiconductor, as it has a very low thermal conductivity (~1 W/m•K) with a high carrier concentration (~1x10²¹ cm^-3). Solid solutions of Yb₁₄MnSb₁₁ with electron donors such as 3+ rare earths for Yb²⁺, Alfor Mn, and Te for Sb, have all shown higher zT’s (1 or higher) by reducing the carrier concentration. In this example, we are able to show that very small amounts (0.01–0.2) of Se doped into Yb₁₄MnSb₁₁ maintains the high carrier concentration and reduces thermal conductivity further. Overall, this results in a zT > 1 at 1200 K. This is an example of an “invisible” dopant that is able to enhance the Seebeck coefficient while keeping a low electrical resistivity and further reducing thermal conductivity. The synthesis, structure, and properties will be presented and discussed in light of current models for such processes.