Department of Physics, University of South Florida, Tampa, Florida 33620, USA.
Inorg Chem. 2012 Aug 20;51(16):8686-92. doi: 10.1021/ic202199t. Epub 2012 Aug 8.
Na(x)Si(136) clathrate-II single crystals with x = 2.9, 5.1, 8.2, and 14.7 were prepared by a two-step process. In the first step, Na(24)Si(136) single crystals were grown from the precursor Na(4)Si(4) by reaction of the vapor phase with spatially separated graphite in a closed volume. In the second step, the Na(24)Si(136) single crystals were subjected to thermal decomposition in a nitrogen atmosphere at 10 Torr and 405 °C. The Na content was controlled by the duration of thermal decomposition. The structural properties were investigated using single-crystal X-ray diffraction and compared with those of single-crystal Na(24)Si(136). The quality of the obtained products also allowed for low-temperature transport property measurements on agglomerates of crystals allowing for an investigation into the low-temperature electrical and thermal properties as a function of Na content.
用两步法制备了 x = 2.9、5.1、8.2 和 14.7 的 Na(x)Si(136)笼型 II 型单晶。在第一步中，通过气相与封闭体积中空间分离的石墨反应，从前驱体 Na(4)Si(4)生长出 Na(24)Si(136)单晶。在第二步中，将 Na(24)Si(136)单晶在 10 托和 405°C 的氮气氛中进行热分解。通过热分解的持续时间来控制 Na 含量。使用单晶 X 射线衍射研究了结构特性，并与单晶 Na(24)Si(136)进行了比较。所得到的产物的质量也允许在低温下对晶体聚集体进行输运性质测量，从而可以研究低温下的电学和热学性质随 Na 含量的变化。
