Local-disorder-induced low thermal conductivity in degenerate semiconductor Cu₂₂Sn₁₀S₃₂

Ventrapati Pavan Kumar (1) , P. Lemoine (2) , Virginia Carnevali (3) , Gabin Guelou (1) , Oleg I Lebedev (1) , Bernard Raveau (1) , Rabih Al Rahal Al Orabi (3) , Marco Fornari (3) , Christophe Candolfi (4) , Carmelo Prestipino (2) , Denis Menut (5, 6) , Bernard Malaman (4) , Jean Juraszek (7) , Koichiro Suekuni (8) , Emmanuel Guilmeau (1)

1 CRISMAT - Laboratoire de cristallographie et sciences des matériaux
2 ISCR - Institut des Sciences Chimiques de Rennes
3 CMU - Central Michigan University
4 IJL - Institut Jean Lamour
5 MARS - Assemblages supramoléculaires et traduction
6 SSOLEIL - Synchrotron SOLEIL
7 GPM - Groupe de physique des matériaux
8 Kyushu University

S-based semiconductors are attracting attention as environmentally friendly materials for energy-conversion applications because of their structural complexity and chemical flexibility. Here, we show that the delicate interplay between the chemical composition and cationic order/disorder allows one to stabilize a new sphalerite derivative phase of cubic symmetry in the Cu-Sn-S diagram: Cu₂₂Sn₁₀S₃₂. Interestingly, its crystal structure is characterized by a semiordered cationic distribution, with the Cu-Sn disorder being localized on one crystallographic site in a long-range-ordered matrix. The origin of the partial disorder and its influence on the electronic and thermal transport properties are addressed in detail using a combination of synchrotron X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, theoretical modeling, and transport property measurements. These measurements evidence that this compound behaves as a pseudogap, degenerate p-type material with very low lattice thermal conductivity (0.5 W m^-1 K^-1 at 700 K). We show that localized disorder is very effective in lowering κ(L) without compromising the integrity of the conductive framework. Substituting pentavalent Sb for tetravalent Sn is exploited to lower the hole concentration and doubles the thermoelectric figure of merit ZT to 0.55 at 700 K with respect to the pristine compound. The discovery of this semiordered cubic sphalerite derivative Cu₂₂Sn₁₀S₃₂ furthers the understanding of the structure-property relationships in the Cu-Sn-S system and more generally in ternary and quaternary Cu-based systems.

Mots clés: Thermoelectric; Sphalerite; Disorder; Degenerate semiconductor; Low thermal conductivity

Domaines: Matériaux; Science des matériaux [cond-mat.mtrl-sci]

Ventrapati Pavan Kumar, P. Lemoine, Virginia Carnevali, Gabin Guelou, Oleg I Lebedev, et al.. Local-disorder-induced low thermal conductivity in degenerate semiconductor Cu₂₂Sn₁₀S₃₂. Inorganic Chemistry, 2021, 60 (21), pp.16273-16285. ⟨10.1021/acs.inorgchem.1c02105⟩. ⟨hal-03414716⟩