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arXiv · 1502.01828

Long-term stability of phase-separated Half-Heusler compounds

Julia Krez·Benjamin Balke·Claudia Felser·Wilfried Hermes·Markus Schwind
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Abstract

Half-Heusler (HH) compounds have shown high Figure of merits up to 1.5. The key to these high thermoelectric efficiencies is an intrinsic phase separation, which occurs in multicomponent Half-Heusler compounds and leads to an significantly reduction of the thermal conductivity. For commercial applications, compatible n- and p-type materials are essential and their thermal stability under operating conditions, e.g. for an automotive up to 873 K, needs to be guaranteed. For the first time, the long-term stability of n- and p-type HH materials is proved. We investigated HH materials based on the Ti0.3Zr0.35Hf0.35NiSn-system after 500 cycles (1700 h) from 373 to 873 K. Both compounds exhibit a maximum Seebeck coefficient of S around 210 muV/K and an intrinsic phase separation into two HH phases. The dendritic microstructure is temperature resistant and maintained the low thermal conductivity values (kappa less than 4 W/Km). Our results emphasize that phase-separated HH compounds are suitable low cost materials and can lead to enhanced thermoelectric efficiencies beyond the set benchmark for industrial applications.

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Julia Krez, Benjamin Balke, Claudia Felser, Wilfried Hermes, Markus Schwind. 2015-02-06. Long-term stability of phase-separated Half-Heusler compounds. https://arxiv.org/abs/1502.01828

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