Thermoelectric Properties of Ga/Ag Codoped Type-III Ba24Ge100 Clathrates with in Situ Nanostructures

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• 作者：Jiefei Fu ; Xianli Su ; Yun Zheng ; Hongyao Xie ; Yonggao Yan ; Xinfeng Tang ; Ctirad Uher
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：September 2, 2015
• 年：2015
• 卷：7
• 期：34
• 页码：19172-19178
• 全文大小：562K
• ISSN：1944-8252

文摘

Because of the low thermal conductivity and high electrical conductivity, type-III Ba₂₄Ge₁₀₀ clathrates are potentially of interest as power generation thermoelectric materials for midto-high temperature operations. Unfortunately, their too high intrinsic carrier concentration results in a quite low Seebeck coefficient. To reduce the carrier concentration, we prepared a series of Ga/Ag codoped type-III Ba₂₄Ge₁₀₀ clathrate specimens by vacuum melting and subsequently compacted by spark plasma sintering (SPS). Doping Ga鈥揂g on the sites of Ge reduces the concentration of electrons and, at higher concentrations, also leads to the in situ formation of BaGe₂ nanoprecipitates detected by the microstructural analysis. As a result of doping, the Seebeck coefficient increases, the thermal conductivity decreases, and the dimensionless figure of merit ZT reaches a value of 0.34 at 873 K, more than three times the value obtained with undoped Ba₂₄Ge_100.