Electronic Structure and Thermoelectric Properties of Noble Metal Clathrates: Ba8M6Ge40(M = Cu, Ag, Au)
Electronic Structure and Thermoelectric Properties of Noble Metal Clathrates: Ba8M6Ge40(M = Cu, Ag, Au)
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贵金属笼形物Ba8M6Ge40(M = Cu, Ag, Au)的电子结构和热电性能
DOI：
10.2320/matertrans.48.684
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发表时间：
2007
影响因子：
1.2
通讯作者：
M. Matsuura
中科院分区：
文献类型：
--
作者：
K. Akai;K. Koga;M. Matsuura
采用第一性原理方法计算了贵金属包合物Ba 8 M 6 Ge 40 (M = Cu, Ag, Au)的电子结构和热电性能，探讨了高性能热电材料的前景。计算的能带结构表明这些笼形化合物是具有p型载流子的简并半导体。带隙因贵金属掺杂而变窄。带隙变窄是由于Ge和M之间的反键性质引起的价带提升以及由于骨架-客体原子通过6d位点的Ba轨道耦合而导致的导带变宽引起的。 Ba 8 M 6 Ge 40 的热电势随温度单调增加，在1000 K下幅度小于100 μV/K。对于高性能热电材料来说，Ba 8 M 6 Ge 40 的载流子浓度稍大。通过改变Ba 8 Au x Ge 46-x 的组成来控制载流子浓度。 Ba 8 Au x Ge 46-x 中的最佳载流子浓度分别为4.4×10 26 m -3 (p型)和6.4×10 26 m -3 (n型)。
Electronic structure and thermoelectric properties of noble metal clathrates Ba 8 M 6 Ge 40 (M = Cu, Ag, Au) were calculated by using a first principle based method to discuss prospect of high performance thermoelectric materials. The calculated band structures show that these clathrate compounds are degenerate semiconductors with p type carrier. The band gaps become narrow by noble metal doping. The band gap narrowing is caused by the valence band lifting due to anti-bonding nature between Ge and M, and conduction band widening due to framework-guest atom coupling via Ba orbitals at 6d sites. The thermoelectric power of Ba 8 M 6 Ge 40 increases with temperatures monotonically and the magnitude is smaller than 100 μV/K under 1000 K. The carrier concentration of Ba 8 M 6 Ge 40 is a little larger for the high performance thermoelectric materials. The carrier concentration is controlled by varying the composition of Ba 8 Au x Ge 46-x . The optimized carrier concentration in Ba 8 Au x Ge 46-x was obtained as 4.4 × 10 26 m -3 (p type) and 6.4 x 10 26 m -3 (n type), respectively.