Off-center rattling and anisotropic expansion of type-I clathrates studied by Raman scattering.
Off-center rattling and anisotropic expansion of type-I clathrates studied by Raman scattering.
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DOI：
10.1103/physrevlett.100.165503
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发表时间：
2008-04
影响因子：
8.6
通讯作者：
Y. Takasu;T. Hasegawa;N. Ogita;M. Udagawa;M. Avila;K. Suekuni;T. Takabatake
中科院分区：
文献类型：
--
作者：
Y. Takasu;T. Hasegawa;N. Ogita;M. Udagawa;M. Avila;K. Suekuni;T. Takabatake
用拉曼散射光谱研究了Sr_8 Ga_（16）Si（30-x）格克斯和Ba_8 Ga_（16）Si（30-x）格克斯中客体离子的动力学运动，以阐明客体振动模式在这些具有异常热输运行为的体系中的作用.观察到的两个系统的客户的能量随着温度的降低而异常减少。Ge掺杂使Sr 8 Ga 16 Si（30-x）格克斯的6d位周围的笼形结构各向异性地扩展，但使Ba 8 Ga 16 Si（30-x）格克斯的6d位周围的笼形结构各向同性地扩展。特别是对于Sr 8 Ga 16 Si（30-x）格克斯，偏离中心的振动与各向异性膨胀同时出现，证实了这些异常对抑制这些系统中的晶格热导率起着至关重要的作用。
Dynamical motions of the guest ions in type-I clathrates Sr8Ga16Si(30-x)Gex and Ba8Ga16Si(30-x)Gex have been studied by Raman scattering spectroscopy, to clarify the role of guest vibration modes in these systems with unusual thermal transport behaviors. An anomalous decrease of the guest energies with decreasing temperature is observed for both systems. The Ge-doping expands the cage surrounding the 6d site anisotropically for Sr8Ga16Si(30-x)Gex, but isotropically for Ba8Ga16Si(30-x)Gex. Especially for Sr8Ga16Si(30-x)Gex, off-center rattling arises simultaneously with the anisotropic expansion, and it is confirmed that these anomalies play a crucial role to suppress lattice thermal conductivity in these systems.