Half-Heusler phase formation and Ni atom distribution in M-Ni-Sn (M = Hf, Ti, Zr) systems

• Published in: Acta materialia Vol. 148; pp. 216 - 224
• Main Authors: Guzik, Matylda N., Echevarria-Bonet, Cristina, Riktor, Marit D., Carvalho, Patricia A., Gunnæs, Anette E., Sørby, Magnus H., Hauback, Bjørn C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-04-2018
• Subjects: Half-Heusler compounds; Phase separation; Powder X-ray diffraction; Solid solution; Thermoelectric materials; Thermoelectric materials; Half-Heusler compounds; Solid solution; Phase separation; Powder X-ray diffraction
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2018.01.019

High resolution synchrotron radiation powder X-ray diffraction (SR-PXD) and scanning transmission electron microscopy (STEM) have been employed for structural characterization of MNiSn, M0.5M′0.5NiSn and M0.5M′0.25M″0.25NiSn (M, M′, M″ = Hf, Ti, Zr) half-Heusler compounds, synthesized by arc melting and thermal annealing. Rietveld refinement results demonstrate that ternary Ti- and Hf-based compositions crystallize with only one half-Heulser phase, while two cubic phases are found in samples with nominal composition ZrNiSn. The performed analysis does not suggest obvious presence of excess Ni in any of the ternary compounds. Instead, it shows disordered distribution of the stoichiometric Ni atoms over 4c and the nominally vacant 4d sites in ZrNiSn as well as formation of Ni vacancies at the 4c site in ZrNi0.98Sn.
[Display omitted]