• Orabi, R. Al Rahal Al
• Juraszek, Jean
• Prestipino, C.
• Fornari, M.
• Carnevali, V.
• Malaman, B.
• Couder, C.
• Lebedev, O. I.
• Lenoir, B.
• Guilmeau, Emmanuel
• Kumar, V. Pavan
• Raveau, B.
• Lemoine, P.
• Guelou, Gabin
• Candolfi, C.

Abstract

In oeder 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

Topics

• impedance spectroscopy
• compound
• cluster
• phase
• transmission electron microscopy
• thermal conductivity
• x-ray absorption spectroscopy
• transport property