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Spacing of close-packed layers as a guidance for symmetry manipulation of IV-VI / Ⅰ-Ⅴ-Ⅵ2 thermoelectrics
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  • Tao Jin,
  • Long Yang,
  • Xinyue Zhang,
  • Wen Li,
  • Yanzhong Pei
Tao Jin
Tongji University
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Long Yang
Tongji University
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Xinyue Zhang
Tongji University
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Wen Li
Tongji University
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Yanzhong Pei
Tongji University

Corresponding Author:[email protected]

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Abstract

The factor that the crystal-structure symmetry in real space can be well inherited in the reciprocal space, leads high-symmetry materials to be top candidates for thermoelectrics due to the possibly resultant high electronic band degeneracy. A general indicator, that can quantitatively describe how crystal structure changes, would help facilitate the advanced thermoelectric material design. For cubic close-packed structures, the spatial environment of the same crystallographic plane family is isotropic, such that the distances between the close-packed layers can be derived from atomic distances within layers. Inspired by this, the relationship between the inter- and intra-layer geometric information can be used for comparing crystal structures with their desired cubic symmetry. The spacing of close-packed layers was found to be an essential indicator for the crystal structure symmetry in Ⅳ-Ⅵ chalcogenides and group I-Ⅴ-VI2 ternary semiconductors, both of which are historically important thermoelectrics. The continuous structure evolution towards high symmetry can be described by the layer spacing when temperature or/and composition change, which is demonstrated by a series of pristine and alloyed thermoelectric materials in this work. The layer spacing based guidance provides a quantitative pathway for manipulating crystal structures to fine tune the electronic band convergence in high-performance thermoelectric materials.