Science China Materials

, Volume 62, Issue 12, pp 1788–1797 | Cite as

Vibration uncoupling of germanium with different valence states lowers thermal conductivity of Cs2Ge3Ga6Se14

  • Ni Ma (马妮)
  • Lin Xiong (熊琳)
  • Ling Chen (陈玲)Email author
  • Li-Ming Wu (吴立明)Email author


The thermal phonon transport is a key matter for heat managing in materials science which is crucial for device miniaturization and power density increase. Herein, we report the synthesis, structure and characterization of a new compound, Cs2Ge3Ga6Se14, with a unique anisotropic structure simultaneously containing Ge3+ and Ge2+ that adopt (Ge1)3+2Se6 dimer or (Ge2)2+Se6 octahedron, respectively. The thermal conductivity was measured to be 0.57–0.48 W m−1 K−1 from 323 to 773 K, the lowest value among all the known Ge containing compounds, approaching its glass limit according to the Cahill’s formulation. More importantly, we discover for the first time that the vibration uncoupling of Ge with different valence states hinders the effective thermal energy transport between the (Ge1)3+2Se6 dimer and (Ge2)2+Se6 octahedron, and consequently lowers the thermal conductivity. In addition, we propose a structure factor fi = sin(180 − β) × dGe−Q/li (i = A, B), with which a structure map of the Cs2Ge3M6Q14 family is given.


Cs2Ge3Ga6Se14 mixed valence states compound thermal conductivity phonon transport crystallography analyses 



热管理是电子器件小型化和功率密度提高的关键, 因此研究材料热输运性质及声子传输机制具有非常重要的意义. 本文报道了一例含多价态锗(Ge3+, Ge2+)的新型硒化物, Cs2Ge3Ga6Se14. 单晶结构衍射数据表明, 化合物中不同价态锗分别采用(Ge3+)2Se6二聚体或(Ge2+)Se6八面体的配位模式, 323–773 K范围内, 其热导率测试值为0.57–0.48 W m−1 K−1, 该值是目前已知含锗固体材料中的最低值, 接近其玻璃态极限值. 更重要的是, 我们发现由于不同价态锗离子振动模式之间存在弱耦合性, 使得热振动能量无法在两种结构单元之间有效传递, 从而降低了化合物热导率. 这种机制在材料热导率研究领域尚属首次发现. 本文还通过结构因子fi=sin(180−βdGe−O/li (i=A, B)的大小, 给出了Cs2Ge3M6Q14家族的晶体结构分布规律.



This research was supported by the National Natural Science Foundation of China (21975032 and 21571020), and the National Key Research and Development Program of China (2018YFA0702100). The room temperature ultrasonic pulse echo measurements were performed by Dr. Yu Xiao and Prof. Li-Dong Zhao from the School of Materials Science and Engineering, Beihang University, Beijing, China. Their great help was sincerely appreciated.

Conflict of interest The authors declare no conflict of interest.

Supplementary material

40843_2019_1192_MOESM1_ESM.pdf (1.1 mb)
Vibration Uncoupling of Germanium with Different Valence States Lowers Thermal Conductivity of Cs2Ge3Ga6Se14


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Copyright information

© Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Beijing Key Laboratory of Energy Conversion and Storage Materials, College of ChemistryBeijing Normal UniversityBeijingChina
  2. 2.Key Laboratory of Theoretical and Computational Chemistry of Ministry of Education, College of ChemistryBeijing Normal UniversityBeijingChina

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