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Structural properties of the thermoelectric material CuCrS2 and of deintercalated CuxCrS2 on different length scales

X-ray diffraction, pair distribution function and transmission electron microscopy studies
: Hansen, Anna-Lena; Dankwort, Torben; Groß, Hendrik; Etter, Martin; König, Jan D.; Düppel, Viola; Kienle, Lorenz; Bensch, Wolfgang


Journal of materials chemistry. C, Materials for optical and electronic devices 5 (2017), No.36, pp.9331-9338
ISSN: 2050-7526
ISSN: 2050-7534
Deutsche Forschungsgemeinschaft DFG
KI 1263/16-1, BE1653/36-1
Journal Article
Fraunhofer IPM ()
thermoelectric material; transmission electron microscopy

We report on the structural alterations of the thermoelectric material CuCrS2 introduced by the removal of 1/3 of the Cu+ ions which are located between CrS2 layers. X-ray diffraction (XRD) and pair distribution function (PDF) analyses revealed a newly formed Cu0.66CrS2 phase with monoclinic symmetry and a 3a superstructure. Simultaneously, a distortion of CrS6 octahedra is observed strongly indicating the oxidation of Cr3+ → Cr4+ leading to a Jahn-Teller distortion. The structural features extracted from XRD indicate a pronounced disorder in the cationic sub-lattice at moderate temperatures (400 K). Transmission electron microscopy (TEM) examination elucidates the formation of a second Cu0.66CrS2 phase without the superstructure, caused by incipient Cu+ mobility upon beam irradiation. The synergetic combination of high temperature XRD and TEM investigations unveiled the complete mechanism of the phase transition occurring at 503 K, where a transformation into the spinel CuCr2S4 and stoichiometric CuCrS2 occurs.