Structure and Thermoelectric Properties of Ba6Ge25−x, Ba6Ge23Sn2, and Ba6Ge22In3: Zintl Phases with a Chiral Clathrate Structure
Structure and Thermoelectric Properties of Ba6Ge25−x, Ba6Ge23Sn2, and Ba6Ge22In3: Zintl Phases with a Chiral Clathrate Structure
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Ba6Ge25−x、Ba6Ge23Sn2 和 Ba6Ge22In3 的结构和热电性能：具有手性笼形结构的 Zintl 相
DOI：
10.1006/jssc.2000.8777
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发表时间：
2000
影响因子：
5.4
通讯作者：
M. Kanatzidis
中科院分区：
文献类型：
--
作者：
Sung‐Jin Kim;Siqing Hu;C. Uher;T. Hogan;Baoquan Huang;J. Corbett;M. Kanatzidis
在830°C的密封石墨管中，通过直接元素化合反应得到了单相Ba 6 Ge 25− x（x <$1）。用单晶X射线衍射法测定了其结构。Ba 6 Ge 25− x采用手性立方空间群P 4 1 32（No.213），维数a =14.5483（2）A，Z =4。该结构由Ba原子为中心的五角十二面体的螺旋链，Ba@Ge 20，和由这些链形成的沸石状笼组成。有空位分布在Ge站点上，得到Ba 6 Ge 24的组合物，其中根据Zintl形式主义的电荷平衡被保留。因此，该化合物满足经典的Zintl概念。Ba 6 Ge 25− x的多晶锭在室温下的电导率为2000 S/cm，塞贝克系数为−18 μV/K。电导率和Seebeck系数在100 K左右出现了一个异常的宽转变。合成了Ba 6 Ge 25− x的三元衍生物Ba 6 Ge 23.32 Sn 1.68和Ba 6 Ge 21.93 In 3.07，并与Ba 6 Ge 25 − x的结构和物理性质进行了比较。
Abstract A single phase of Ba 6 Ge 25− x ( x ∼1) was obtained from a direct element combination reaction in a sealed graphite tube at 830°C. Its structure was determined by single-crystal X-ray diffraction methods. Ba 6 Ge 25− x adopts the chiral cubic space group P 4 1 32 (No. 213) with dimensions of a =14.5483(2) A and Z =4. The structure consists of helical chains of Ba atom-centered pentagonal dodecahedra, Ba@Ge 20 , and zeolite-like cages formed by those chains. There are vacancies distributed over the Ge sites giving a composition of Ba 6 Ge 24 , in which charge balance according to the Zintl formalism is retained. The compound therefore satisfies the classical Zintl concept. Polycrystalline ingots of Ba 6 Ge 25− x showed an electrical conductivity of 2000 S/cm and a Seebeck coefficient of −18 μV/K at room temperature. An anomalous broad transition in the electrical conductivity and Seebeck coefficient was observed at ∼100 K. Ba 6 Ge 23.32 Sn 1.68 and Ba 6 Ge 21.93 In 3.07 as ternary derivatives of Ba 6 Ge 25− x were also synthesized and their structural and physical properties compared with those of Ba 6 Ge 25− x .