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DS: Fachverband Dünne Schichten

DS 42: Thermoelectric Materials

DS 42.9: Vortrag

Donnerstag, 3. April 2014, 17:15–17:30, CHE 89

Half Heusler compounds as high performance thermoelectric materials — •J Schmitt^{1, 2}, Z Gibbs², J Snyder², and C Felser^1,3 — ¹Institute for Inorganic and Analytical Chemistry, Johannes Gutenberg-University, Mainz, Germany — ²Materials Science, California Institute of Technology, Pasadena, USA — ³Max Planck Institute for Chemical Physics of Solids, Dresden, Germany

Half Heusler compounds with the general formula XNiSn crystalize in a C1_b cubic structure. They are considered to be promising thermoelectric materials because of their low costs and they consist of environmentally friendly elements. Those with 18 valence electrons are expected to be narrow band gap semiconductors. Numerous compounds have been studied focusing on their high thermoelectric properties. The majority of these materials in the class of XNiSn-systems are n-type thermoelectrics. In this study we investigated the thermoelectric behavior of the Zr_1−xSc_xNiSn (x<0.15) solid solutions, a p-type counterpart of the high zT n-type ZrNiSn family. Measurements of the carrier concentration, Hall mobility, electrical resistivity, thermal diffusivity and thermopower were measured up to 850K. The substitution of Zirconium by Scandium, which possesses one valence electron less, lead to a domination of holes as charge carriers changing the sign for the Seebeck coefficient and the Hall carrier concentration. From the Hall measurements lower mobilities as expected were observed. This observation can be understood within the model of mixed conduction, leading to a depression of the thermopower or bipolar effects in thermal transport measurements.