Copper‐Rich Thermoelectric Sulfides: Size‐Mismatch Effect and Chemical Disorder in the [TS4]Cu6 Complexes of Cu26T2Ge6S32 (T=Cr, Mo, W) Colusites

Herein, we investigate the Mo and W substitution for Cr in synthetic colusite, Cu26Cr2Ge6S32. Primarily, we elucidate the origin of extremely low electrical resistivity which does not compromise the Seebeck coefficient and leads to outstanding power factors of 1.94 mW m−1 K−2 at 700 K in Cu26Cr2Ge6S...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2019-10, Vol.58 (43), p.15455-15463
Main Authors: Pavan Kumar, Ventrapati, Guélou, Gabin, Lemoine, Pierric, Raveau, Bernard, Supka, Andrew R., Al Rahal Al Orabi, Rabih, Fornari, Marco, Suekuni, Koichiro, Guilmeau, Emmanuel
Format: Article
Language:English
Subjects:
Cations
Chemical Sciences
Chromium
colusites
Coordination chemistry
Copper
Cristallography
disorder
Electrical resistivity
Electron transport
Material chemistry
mismatch
Molybdenum
Organic chemistry
Seebeck effect
Substitutes
sulfides
Tetrahedra
thermoelectric properties
Transport properties
Tungsten
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Summary:Herein, we investigate the Mo and W substitution for Cr in synthetic colusite, Cu26Cr2Ge6S32. Primarily, we elucidate the origin of extremely low electrical resistivity which does not compromise the Seebeck coefficient and leads to outstanding power factors of 1.94 mW m−1 K−2 at 700 K in Cu26Cr2Ge6S32. We demonstrate that the abnormally long iono‐covalent T–S bonds competing with short metallic Cu–T interactions govern the electronic transport properties of the conductive “Cu26S32” framework. We address the key role of the cationic size‐mismatch at the core of the mixed tetrahedral–octahedral complex over the transport properties. Two essential effects are identified: 1) only the tetrahedra that are directly bonded to the [TS4]Cu6 complex are significantly distorted upon substitution and 2) the major contribution to the disorder is localized at the central position of the mixed tetrahedral–octahedral complex, and is maximized for x=1, i.e. for the highest cationic size‐variance, σ2. Cation‐size mismatch within mixed octahedral–tetrahedral complexes disturbs the electrical transport properties of colusites. The direct relationship between size‐mismatch effect, structural disorder, and chemical bonding in the conductive “Cu26S32” framework has been established and correlated with the thermoelectric properties.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201908579