title: Multi-temperature synchrotron PXRD and physical properties study of half-Heusler TiCoSb.
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 × 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 μV K(-1) was found at 400 K, but the substantial thermal conductivity (∼10 W mK(-1) at 400 K) leads to a moderate thermoelectric figure of merit of 0.025 at 400 K.
authors.affiliation: Center for Materials Crystallography, Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000, Aarhus C, Denmark.
authors.forename: I
authors.initials: I
authors.lastname: Skovsen
authors.forename: L
authors.initials: L
authors.lastname: Bjerg
authors.forename: M
authors.initials: M
authors.lastname: Christensen
authors.forename: E
authors.initials: E
authors.lastname: Nishibori
authors.forename: B
authors.initials: B
authors.lastname: Balke
authors.forename: C
authors.initials: C
authors.lastname: Felser
authors.forename: B B
authors.initials: BB
authors.lastname: Iversen