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

低热导率新机制——Cs2Ge3Ga6Se14中异价锗离子的振动弱耦合性（英文）

作　　者：Ni Ma Lin Xiong Ling Chen Li-Ming Wu 马妮;熊琳;陈玲;吴立明(Beijing Key Laboratory of Energy Conversion and Storage Materials,College of Chemistry,Beijing Normal University,Beijing 100875,China;Key Laboratory of Theoretical and Computational Chemistry of Ministry of Education,College of Chemistry,Beijing Normal University,Beijing 100875,China)

机构地区：[1]Beijing Key Laboratory of Energy Conversion and Storage Materials,College of Chemistry,Beijing Normal University,Beijing 100875,China [2]Key Laboratory of Theoretical and Computational Chemistry of Ministry of Education,College of Chemistry,Beijing Normal University,Beijing 100875,China

出　　处：《Science China Materials》2019年第12期1788-1797,共10页中国科学（材料科学（英文版）

基　　金：supported by the National Natural Science Foundation of China (21975032 and 21571020);the National Key Research and Development Program of China (2018YFA0702100)

摘　　要：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 Ge^3+ and Ge^2+ that adopt(Ge1)2^3+ Se6 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)2^3+ Se6 dimer and(Ge2)^2+Se6 octahedron, and consequently lowers the thermal conductivity. In addition, we propose a structure factor f = sin(180) ×d/l(i =A, B)iGe Qi, with which a structure map of the Cs2 Ge3 M6 Q14 family is given.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(Ge^3+, Ge^2+)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(Ge^3+)2Se6二聚体或(Ge^2+)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^-1K^-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-β)×dGe–O/li(i=A, B)的大小,给出了Cs2Ge3M6Q14家族的晶体结构分布规律.

关 键 词：Cs2Ge3Ga6Se14 mixed valence states compound thermal conductivity phonon transport crystallography analyses 

分 类 号：G63[文化科学—教育学]