Multi-temperature synchrotron PXRD and physical properties study of 
half-Heusler TiCoSb

Skovsen, I.; Bjerg, L.; Christensen, M.; Nishibori, E.; Balke, B.; Felser, C.; Iversen, B. B.

doi:10.1039/c0dt00742k

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Multi-temperature synchrotron PXRD and physical properties study of half-Heusler TiCoSb

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Skovsen, I., Bjerg, L., Christensen, M., Nishibori, E., Balke, B., Felser, C., et al. (2010). Multi-temperature synchrotron PXRD and physical properties study of half-Heusler TiCoSb. Dalton Transactions, 39(42), 10154-10159. doi:10.1039/c0dt00742k.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0018-B5F7-8

Abstract

Phase pure samples of the half-Heusler material TiCoSb were synthesised and investigated. Multi-temperature synchrotron powder X-ray diffraction (PXRD) data measured between 90 and 1000 K in atmospheric air confirm the phase purity, but they also reveal a decomposition reaction starting at around 750 K. This affects the high temperature properties since TiCoSb is semiconducting, whereas CoSb is metallic. Between 90 K and 300 K the linear thermal expansion coefficient is estimated to be 10.5 x 10(-6) K(-1), while it is 8.49 10(-6) K(-1) between 550 K and 1000 K. A fit of a Debye model to the Atomic Displacement Parameters obtained from Rietveld refinement of the PXRD data gives a Debye temperature of 395(4) K. The heat capacity was measured between 2 K and 300 K and a Debye temperature of 375(5) K was obtained from modelling of the data. Coming from low temperatures the electrical resistivity shows a metallic to semiconducting transition at 113 K. A relatively high Seebeck coefficient of -250 mu VK(-1) was found at 400 K, but the substantial thermal conductivity (similar to 10 W mK(-1) at 400 K) leads to a moderate thermoelectric figure of merit of 0.025 at 400 K.