Short and long range order of Half-Heusler phases in (Ti,Zr,Hf)CoSb thermoelectric compounds

The structural properties of (Ti,Zr,Hf)CoSb thermoelectric Half-Heusler compounds were investigated by synchrotron radiation based techniques. The short-range order, in particular the environment of the Co atoms, was studied by extended X-Ray absorption fine structure spectroscopy and the long range order by powder X-Ray diffraction. Structural models were obtained for the single phase materials TiCoSb_0.85Sn_0.15, ZrCoSb_0.85Sn_0.15, and HfCoSb_0.85Sn_0.15. These models were transferred for the phase-separated material Ti_0.5Hf_0.5CoSb_0.85Sn_0.15. As a result, proving that each Half-Heusler phase was well ordered, apart from the intermixing of Ti and Hf on its designated crystallographic lattice site.