Atomic Interactions in the p-Type Clathrate I Ba8Au5.3Ge40.7

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• 作者：Hui Zhang ; Horst Borrmann ; Niels Oeschler ; Christophe Candolfi ; Walter Schnelle ; Marcus Schmidt ; Ulrich Burkhardt ; Michael Baitinger ; Jing-Tai Zhao ; Yuri Grin
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：February 21, 2011
• 年：2011
• 卷：50
• 期：4
• 页码：1250-1257
• 全文大小：970K
• 年卷期：v.50,no.4(February 21, 2011)
• ISSN：1520-510X

文摘

Single crystals of Ba₈Au_5.3Ge_40.7 [space group Pm3̅n (No. 223), a = 10.79891(8) 脜] were prepared by a Bridgman technique. The crystal structure refinement based on single-crystal X-ray diffraction data does not reveal any vacancies in the Au/Ge framework or in the cages. In addition to the ionic bonding between Ba and the anionic framework, a direct interaction between Ba and Au atoms was identified in Ba₈Au_5.3Ge_40.7 by applying the electron localizability indicator. As expected by the chemical-bonding picture, Ba₈Au_5.3Ge_40.7 is a diamagnet and shows p-type electrical conductivity with a hole carrier concentration of 7.14 脳 10¹⁹ cm^鈭? at 300 K and very low lattice thermal conductivity of 鈮?.6 W m^鈭? K^鈭? at 500 K. The thermoelectric figure of merit ZT of single crystals of Ba₈Au_5.3Ge_40.7 attains 0.3 at 511 K and reaches 0.9 at 680 K in a polycrystalline sample of closely similar composition. This opens up an opportunity for tuning of the thermoelectric properties of materials in the Ba鈭扐u鈭扜e clathrate system by changing the chemical composition.