Condron Cathie L, Kauzlarich Susan M, Nolas G S
Department of Chemistry, University of California Davis, One Shields Avenue, Davis, California 95616, USA.
Inorg Chem. 2007 Apr 2;46(7):2556-62. doi: 10.1021/ic062115v. Epub 2007 Feb 7.
Single crystals of AxBa8-xAl14Si31 (A = Sr, Eu) were grown using a molten Al flux technique. Single-crystal X-ray diffraction confirms that AxBa8-xAl14Si31 (A = Sr, Eu) crystallize with the type I clathrate structure, and phase purity was determined with powder X-ray diffraction. Stoichiometry was determined to be Sr0.7Ba7.3Al14Si31 and Eu0.3Ba7.7Al14Si31 by electron microprobe analysis. These AxBa8-xAl14Si31 phases can be described as framework-deficient clathrate type I structures with the general formula, AxBa8-xAlySi42-3y/4[]4-1/4y. DSC measurements indicate that these phases melt congruently at 1413 and 1415 K for Sr0.7Ba7.3Al14Si31 and Eu0.3Ba7.7Al14Si31, respectively. Temperature-dependent resistivity indicates metallic behavior, and the negative Seebeck coefficient indicates transport processes dominated by electrons as carriers. Thermal conductivity of these phases remains low with Sr0.7Ba7.3Al14Si31 having the lowest values.
采用熔融铝助熔剂法生长了AxBa8-xAl14Si31（A = Sr，Eu）的单晶。单晶X射线衍射证实AxBa8-xAl14Si31（A = Sr，Eu）以I型包合物结构结晶，并用粉末X射线衍射确定了相纯度。通过电子微探针分析确定化学计量比为Sr0.7Ba7.3Al14Si31和Eu0.3Ba7.7Al14Si31。这些AxBa8-xAl14Si31相可描述为具有通式AxBa8-xAlySi42-3y/4[]4-1/4y的骨架缺陷型I型包合物结构。差示扫描量热法测量表明，对于Sr0.7Ba7.3Al14Si31和Eu0.3Ba7.7Al14Si31，这些相分别在1413 K和1415 K时完全熔化。与温度相关的电阻率表明其具有金属行为，负塞贝克系数表明以电子作为载流子的输运过程占主导。这些相的热导率仍然较低，其中Sr0.7Ba7.3Al14Si31的值最低。
