Abstract
Thermal conductivity is one of the most fundamental properties of materials with the value being determined by nearly all-scale structural features and multiple physical processes. Rapidly judging material’s thermal conductivity is extremely important but challenging for the applications. The material genome paradigm offers a revolutionary way to efficiently screen and discover materials with designed properties by using accessible indicators. But such a performance indicator for thermal conductivity is quite difficult to propose due to the existence of multiple mechanisms and processes, especially for the materials with complex structures such as chalcogenides. In this study, the number mismatch between cations and anions is proposed as a practical performance indicator for lattice thermal conductivity in complex copper and silver chalcogenides, which can be used to explain the observed experimental data and find new low thermal conductivity materials. Such a number mismatch brings about rich phenomena to affect thermal conductivity including the complication of the unit cell and the creation of chemical hierarchy, point defects, rattling modes and lone-pair electrons. It is expected that this rich-connotation performance indicator can be also extended to other complex materials to discover designed thermal conductivities.
Highlights
Thermal conductivity (κ) is a material’s basic property that is used to characterize its heat conducting capability
We report that the number mismatch (δ) between cations (Ncation) and anions (Nanion), δ = (Ncation − Nanion)/Nanion, can be regarded as the simple performance indicator to quickly and directly explain and discover materials with low lattice thermal conductivity in complex chalcogenides
Tetrahedrite Cu12Sb4S13 has a δ of 0.23 and a low κL about 0.65 W m−1 K−1 at room temperature[26,27]. All these detailed mechanisms of suppressing κL can be included in the simple performance indicator δ, which is schematically depicted in Fig. 4a, b and will be expanded in the part
Summary
Thermal conductivity (κ) is a material’s basic property that is used to characterize its heat conducting capability. In chalcogenides, chemical bonding inequality, and hierarchy are diverse, leading to various factors affecting thermal transport such as abundant intrinsic defects, loose bonding, lone-pair, and rattling atoms. They are likely to coexist and interact with each other. We report that the number mismatch (δ) between cations (Ncation) and anions (Nanion), δ = (Ncation − Nanion)/Nanion, can be regarded as the simple performance indicator to quickly and directly explain and discover materials with low lattice thermal conductivity (κL) in complex chalcogenides. New low-κL materials such as Cu2Sn4S9 are screened by the proposed large number mismatch between cations and anions, and confirmed by experiment (Fig. 1)
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