Promoted crystallisation and cationic ordering in thermoelectric Cu 26 V 2 Sn 6 S 32 colusite by eccentric vibratory ball milling

Michal Hegedüs (1) , Marcela Achimovičová (2) , Hongjue Hui (3) , Gabin Guelou (3) , P. Lemoine (4) , Ismail Fourati (5) , Jean Juraszek (5) , B. Malaman (6) , Peter Baláž (2) , Emmanuel Guilmeau (3)

1 Synthon
2 SAS - Slovak Academy of Sciences
3 CRISMAT - Laboratoire de cristallographie et sciences des matériaux
4 ISCR - Institut des Sciences Chimiques de Rennes
5 GPM - Groupe de physique des matériaux
6 IJL - Institut Jean Lamour

A pristine colusite Cu26V2Sn6S32 was successfully synthesised on a 100 g scale via mechanochemical reaction in an industrial eccentric vibratory ball mill followed by spark plasma sintering (SPS) at 873 K. The milling of elemental precursors from 1 up to 12 hours was performed and the prepared samples were investigated in details by X-ray powder diffraction, Mössbauer spectroscopy, scanning electron microscopy, and thermoelectric property measurements. The results point to the formation of a high purity and high crystallinity non-exsoluted colusite phase after SPS process (4 # 3 , a = 10.7614(1) Å) in the case of a 12 h A c c e p t e d M a n u s c r i p t milled sample. In comparison, samples milled for 1-6 h displayed small quantities of binary Cu-S phases and vanadium core-shell inclusions, leading to a V-poor/Sn-rich colusite with higher degree of structural disorder. These samples exhibit lower electrical conductivity and Seebeck coefficient while an increase in the total thermal conductivity is observed. This phenomenon is explained by a higher reactivity and grain size reduction upon prolonged milling and by a weak evolution of the chemical composition from a partly disordered V-poor/Sn-rich colusite phase to a well-ordered stoichiometric Cu26V2Sn6S32 colusite, which leads to a decrease in carrier concentration. For all samples, the calculated PF values, around 0.7-0.8 mW m-1 K-2 at 700 K, are comparable to the values previously achieved for mechanochemically synthesised Cu26V2Sn6S32 in laboratory mills. This approach thus serves as an example of scaling-up possibility for sulphur-based TE materials and supports their future large-scale deployment.

Domains: Physics [physics]; Condensed Matter [cond-mat]; Materials Science [cond-mat.mtrl-sci]

Michal Hegedüs, Marcela Achimovičová, Hongjue Hui, Gabin Guelou, P. Lemoine, et al.. Promoted crystallisation and cationic ordering in thermoelectric Cu 26 V 2 Sn 6 S 32 colusite by eccentric vibratory ball milling. Dalton Transactions, 2020, 49 (44), pp.15828-15836. ⟨10.1039/D0DT03368E⟩. ⟨hal-02997011⟩