Long-Range Cationic Order Collapse Triggered by S/Cl Mixed-Anion Occupancy Yields Enhanced Thermoelectric Properties in Cu5Sn2S7

Gabin Guélou, Ventrapati Pavan Kumar, Virginia Carnevali, Oleg I. Lebedev, Bernard Raveau, Christophe Couder, Carmelo Prestipino, Pierric Lemoine, Bernard Malaman, Jean Juraszek, Christophe Candolfi, Bertrand Lenoir, Rabih Al Rahal Al Orabi, Marco Fornari, Emmanuel Guilmeau

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

To investigate pathways to adjust the charge carrier concentration and optimize the thermoelectric properties, we characterized structural properties, thermal stability, and thermoelectric performance of pristine and Cl-doped Cu5+ϵSn2-ϵS7. We demonstrate that Cl doping in Cu5Sn2S7-type monoclinic compounds induces a collapse of the long-range cationic ordering, ultimately leading to a sphalerite-type cubic phase characterized by ordered [Sn(S,Cl)4]x clusters. The change in crystal structure symmetry upon Cl doping is analyzed by Rietveld refinements against X-ray powder diffraction data, transmission electron microscopy, Mössbauer and X-ray absorption spectroscopy, and low-and high-temperature transport property measurements. The thermoelectric properties of the so-obtained cubic sphalerite Cu5+ϵSn2-ϵS7-yCly (0 ≤ ϵ ≤ 0.133, y = 0.35, 0.70) are strongly enhanced with respect to the undoped Cu5Sn2S7: the power factor improves slightly while both electronic and lattice contributions to the thermal conductivity are reduced. Overall, single-phase Cl-doped Cu5.133Sn1.866S7-yCly (y = 0.35, 0.70) compounds exhibit high thermoelectric performance, reaching a maximum ZT of 0.45 at 670 K.

Original languageEnglish
Pages (from-to)9425-9438
Number of pages14
JournalChemistry of Materials
Volume33
Issue number23
DOIs
StatePublished - Dec 14 2021

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