Promoted crystallisation and cationic ordering in thermoelectric Cu26V2Sn6S32 colusite by eccentric vibratory ball milling. Issue 44 (6th November 2020)

• Record Type: Journal Article
• Authors: Hegedüs, Michal; Achimovičová, Marcela; Hui, Hongjue; Guélou, Gabin; Lemoine, Pierric; Fourati, Ismail; Juraszek, Jean; Malaman, B.; Baláž, Peter; Guilmeau, Emmanuel
• Is Part Of: Dalton transactions. Volume 49:Issue 44(2020)
• Page Start: 15828
• Page End: 15836
• Publication Date: 2020-11-06
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d0dt03368e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The impact of eccentric vibratory ball milling time on the crystallisation of thermoelectric Cu26 V2 Sn6 S32 is addressed. Mössbauer spectroscopy is confirmed as a powerful technique to investigate local cationic order/disorder in ball-milled colusites. Abstract : A pristine colusite Cu26 V2 Sn6 S32 was successfully synthesised on a 100 g scale via a 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 detail 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 the SPS process ( P 4̄3 n, a = 10.7614(1) Å) in the case of a 12 h 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 a 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 Cu26 V2 Sn6 S32 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 Cu26 V2 Sn6 S32 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.