Crystal Structure Classification of Copper‐Based Sulfides as a Tool for the Design of Inorganic Functional Materials

Abstract

Research focusing on the interplay between structural features and transport properties of inorganic materials is of paramount importance for the identification, comprehension, and optimisation of functional materials. In this respect, Earth‐abundant copper sulfides have been receiving considerable attention from scientists as the urgency remains to discover and improve the efficiency of sustainable materials for energy applications. This proposed classification of copper sulfides, associated with p‐ and/or d‐block elements, is based on their crystallographic features and an analysis of their transport properties. It provides guidelines to help estimate some properties of new materials (type of main charge carriers, thermal conductivity, transport mechanisms, etc.) from consideration of only their chemical composition and crystal structure. The classification relies primarily on recent studies in the fields of thermoelectricity and photovoltaics as well as on crystal‐structure investigations.

Local-Disorder-Induced Low Thermal Conductivity in Degenerate Semiconductor Cu22Sn10S32

“…The weak residual electronic density determined from the refinement suggests that no atoms are located at the “interstitial” position of the sphalerite framework. This indicates that Cu 22 Sn 10 S 32 is a group A phase, referring to copper-based sulfides classification . The conditions of data collection and structure refinement are summarized in Table and the refined crystallographic data in Table S1.…”

“…The interatomic distances in the cubic Cu 22 Sn 10 S 32 phase, calculated from Rietveld refinement of the synchrotron PXRD data and from refinement of the single-crystal XRD data, are gathered in Tables and S2, respectively. These values are in agreement with those encountered in sphalerite derivative copper sulfides, i.e., 2.30−2.33 Å for Cu–S and 2.41 Å for Sn–S . Moreover, the average interatomic distances of 2.36 Å determined between metals on the 12 f site (i.e., M4) and S atoms, intermediate between the Cu–S and Sn–S distances, confirm occupation of the site by both Cu and Sn atoms.…”

“…This indicates that Cu 22 Sn 10 S 32 is a group A phase, referring to copper-based sulfides classification. 3 The conditions of data collection and structure refinement are summarized in Table 2 and the refined crystallographic data in Table S1. The interatomic distances in the cubic Cu 22 Sn 10 S 32 phase, calculated from Rietveld refinement of the synchrotron PXRD data and from refinement of the single-crystal XRD data, are gathered in Tables 3 and S2, respectively.…”

“…They are mainly p-type conductors formed with non-toxic, ecofriendly, and Earth abundant elements. [1][2][3] Several CTS with chemical formula Cu2+xSn1-xS3 have been synthesized to date and have been shown to exhibit attractive electronic and thermal properties: Cu2SnS3 (x = 0), 1,4 Cu7Sn3S10 (x ~ 0.10), 5 Cu5Sn2S7 (x ~ 0.15), 6 Cu3SnS4 (x = 0.25) 7,8 .…”

“…Copper–tin sulfides (CTS) are an interesting family of compounds with applications in thermoelectricity and photovoltaics. They are mainly p-type conductors formed with nontoxic, ecofriendly, and Earth-abundant elements. − Several CTS with the chemical formula Cu 2+ x Sn 1– x S 3 have been synthesized to date and have been shown to exhibit attractive electronic and thermal properties: Cu 2 SnS 3 ( x = 0), , Cu 7 Sn 3 S 10 ( x ∼ 0.10), Cu 5 Sn 2 S 7 ( x ∼ 0.15), and Cu 3 SnS 4 ( x = 0.25). , The thermoelectric performance of these materials, quantified by the dimensionless thermoelectric figure of merit ZT = S 2 T /ρκ ( T is the operating temperature, S the Seebeck coefficient, ρ the electrical resistivity, and κ the thermal conductivity), is highly dependent on the details of the chemical bonding as well as the cationic distribution in the CTS conductive framework (order–disorder phenomena). For instance, the prototypical Cu 2 SnS 3 ( x = 0) reaches competitive TE performances when doped with Zn and Co, leading to ZT values of 0.58 and 0.85 at 723 K, respectively. , Although all of the aforementioned compounds derive from the ZnS sphalerite structure, they differ from each other by significant structural distortions and cationic orderings, which critically influence their transport properties.…”