Structure and Raman scattering study on Ba8GaxSi46−x (x=10 and 16) type I clathrates
Structure and Raman scattering study on Ba8GaxSi46−x (x=10 and 16) type I clathrates
复制标题
Ba8GaxSi46−x (x=10 和 16) I 型包合物的结构和拉曼散射研究
DOI：
10.1016/j.jssc.2004.01.011
复制
发表时间：
2004
影响因子：
3.3
通讯作者：
J. Nagao
中科院分区：
文献类型：
--
作者：
D. Nataraj;J. Nagao
用X射线衍射法和拉曼散射法研究了Ba4 6-x包合物(x=10和16)的结构和振动性质。随温度变化的电阻率测量表明，该包合物具有半导体性质，能带隙为0.31 eV。另一方面，对Ba{sub8}Ga{sub16}Si{sub30}的测量表明，该笼合物具有类似金属的导电性。结果表明，Ba3+的半导电性是由于骨架中的空位无序引起的。室温拉曼散射测量解析了几个拉曼振动模，其中包括与Ba原子的摇摆运动对应的低频拉曼振动模。结果表明，Ba在各包合物中的低频位置分别为49.4、73.7和97.3 cm{sup-1}(BaB 8}Ga{sub10}Si{sub36})和43.7、74.5和92.4 cm{sup-1}(Ba{sub8}Ga{sub16}Si{sub30})，这与已报道的密度泛函(DF)计算得到的Ba的低频模式相一致。骨架、镓的差异和空位无序影响了频率模的位置和宽度。室温晶格热导率分别为1.128和1.071 Wm{sup-1}K{sup-1}，这主要归因于骨架声学和Ba拍振模之间的共振散射。
Structure and vibrational properties of Ba{sub 8}Ga{sub x}Si{sub 46-x} (x=10 and 16) clathrates were studied by X-ray diffraction and Raman scattering measurements. The temperature dependent electrical resistivity measurement on Ba{sub 8}Ga{sub 10}Si{sub 36} has shown semiconducting nature of that clathrate with an energy band gap value of 0.31 eV. On the other hand the measurement on Ba{sub 8}Ga{sub 16}Si{sub 30} has shown metallic like electrical conductivity of that clathrate. The origin of semiconductivity in Ba{sub 8}Ga{sub 10}Si{sub 36} was found to be due to the vacancy disorder in the framework sites. Room temperature Raman scattering measurements resolved several Raman vibrational modes, including low frequencies ones corresponding to the rattling motion of Ba atoms. The low frequency positions of Ba in the respective clathrates at 49.4, 73.7 and 97.3 cm{sup -1} for Ba{sub 8}Ga{sub 10}Si{sub 36} and at 43.7, 74.5 and 92.4 cm{sup -1} for Ba{sub 8}Ga{sub 16}Si{sub 30} were found to be in agreement with the reported density functional (DF) calculated low frequency modes of Ba{sub 8}Ga{sub 16}Si{sub 30}. The framework gallium difference and vacancy disorders were found to influence the position and widths of frequency modes. Room temperature lattice thermal conductivity of Ba{sub 8}Ga{sub 10}Si{sub 36} and Ba{sub 8}Ga{sub 16}Si{sub 30} were 1.128 and 1.071 Wm{sup -1} K{sup -1}, respectively, and this low value was attributed to the resonant scattering between the framework acoustic and Ba rattling modes.