Cationic clathrate I Si(46-x)P(x)Te(y) (6.6(1) < or = y < or = 7.5(1), x < or = 2y): crystal structure, homogeneity range, and physical properties.
Cationic clathrate I Si(46-x)P(x)Te(y) (6.6(1) < or = y < or = 7.5(1), x < or = 2y): crystal structure, homogeneity range, and physical properties.
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阳离子包合物 I Si(46-x)P(x)Te(y) (6.6(1) < 或 = y < 或 = 7.5(1), x < 或 = 2y)：晶体结构、均匀性范围和物理性质
DOI：
10.1021/ic8023887
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发表时间：
2009
影响因子：
4.6
通讯作者：
A. Shevelkov
中科院分区：
文献类型：
--
作者：
J. Zaikina;K. Kovnir;U. Burkhardt;W. Schnelle;F. Haarmann;U. Schwarz;Y. Grin;A. Shevelkov
由这些元素合成了一种新的阳离子包合物I Si（46-x）P（x）Te（y）（6.6（1）< or = y < or = 7.5（1），x < or = 2 y，1375 K）），并通过X射线粉末衍射、热分析、扫描电子显微镜、波长色散X射线光谱（WDXS）、中子粉末衍射和（31）P核磁共振光谱进行了表征。研究了样品的磁化率和电阻率的热行为。Si（46-x）P（x）Te（y）显示出宽的均匀性范围，这是由于在笼形物I结构的较小笼内的碲客体位置中存在空位。Si（46-x）P（x）Te（y）结构中的空位有序导致空间群从Pm 3 n（理想笼形物I）变为Pm 3，并伴随着P和Si原子在不同骨架位置上的重新分布。中子粉末衍射证实，P原子优选地在含空位的碲客体位置周围形成笼。此外，（31）P NMR自旋-自旋弛豫实验揭示了磷原子具有不同配位的位点的存在。用WDXS精确测定Si（46-x）P（x）Te（y）的组成，发现磷含量与Zintl计数方案（x = 2 y）有微小但明显的偏差（x ≤ 2 y）。该化合物是抗磁性的，而电阻率测量显示激活行为或重掺杂半导体。热分析表明，所研究的包合物具有很高的稳定性：Si（46-x）P（x）Te（y）在真空中约1460 K时发生不一致熔化，在空气中直至1295 K仍保持稳定，不会发生氧化。
A new cationic clathrate I Si(46-x)P(x)Te(y) (6.6(1) < or = y < or = 7.5(1), x < or = 2y at 1375 K) was synthesized from the elements and characterized by X-ray powder diffraction, thermal analysis, scanning electron microscopy, wavelength dispersive X-ray spectroscopy (WDXS), neutron powder diffraction, and (31)P NMR spectroscopy. The thermal behaviors of the magnetic susceptibility and resistivity were investigated as well. Si(46-x)P(x)Te(y) reveals a wide homogeneity range due to the presence of vacancies in the tellurium guest positions inside the smaller cage of the clathrate I structure. The vacancy ordering in the structure of Si(46-x)P(x)Te(y) causes the change of space group from Pm3n (ideal clathrate I) to Pm3 accompanied by the redistribution of P and Si atoms over different framework positions. Neutron powder diffraction confirmed that P atoms preferably form a cage around the vacancy-containing tellurium guest position. Additionally, (31)P NMR spin-spin relaxation experiments revealed the presence of sites with different coordination of phosphorus atoms. Precise determination of the composition of Si(46-x)P(x)Te(y) by WDXS showed slight but noticeable deviation (x < or = 2y) of phosphorus content from the Zintl counting scheme (x = 2y). The compound is diamagnetic while resistivity measurements show activated behavior or that of heavily doped semiconductors. Thermal analysis revealed high stability of the investigated clathrate: Si(46-x)P(x)Te(y) melts incongruently at approximately 1460 K in vacuum and is stable in air against oxidation up to 1295 K.