Structure and Properties of Hydrogenated Ca, Sr, Ba, and Eu Silicides.
Structure and Properties of Hydrogenated Ca, Sr, Ba, and Eu Silicides.
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氢化钙、锶、钡和铕硅化物的结构和性能。
DOI：
10.1002/chin.200952002
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
R. Nesper
中科院分区：
文献类型：
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作者：
M. Armbruster;M. Woerle;F. Krumeich;R. Nesper
以CrB型结晶的二元金属硅化物CaSi、BaSi、SrSi和EuSi可逆地吸收氢。采用载气热萃取法测定产物氢含量（CaSiHx: 1.56 wt %,x≈︁ 1.06; SrSiHx: 1.35 wt %,x≈︁ 1.6; BaSiHx: 2.08 wt %,x≈︁ 3.4; EuSiHx: 0.99 wt %,x≈︁ 1.8）。根据同步热重、DTA 和质谱分析，不同氢化物的脱氢开始于 BaSiHx 的温度为 610 K、CaSiHx 和 SrSiHx 的温度为 675 K、EuSiHx 的脱氢温度为 640 K。 BaSiHx 分别在 765 K 和 1000 K 下进一步释放氢，CaSiHx 在 760 K 下进一步释放氢。通过 SEM 和 X 射线衍射检测并全面表征了硅化物氢化引起的基本形态和结构变化。根据XRD结果，MSiHx(M= Ca、Ba、Sr、Eu)相的晶体结构均为斜方晶系(空间群Pnma)。晶格参数从CaSi中的a= 4.559(1) Å,b= 10.731(1) Å,c= 3.890(1) Å (空间群Cmcm,Z= 1)变为a= 14.4884(9) Å,b= 3.8247(1) Å,c= 11.2509(5) Å (Z= 3) CaSiHx 由氢吸收引起，诱导沿轴形成三重上层结构。在CaSiHx中，[Sin]2-之字形链的平面是倾斜的，并且链间Si-Si接触形式上形成对应于Si-的氧化。通过原位 X 射线衍射研究研究了氢解吸过程，结果表明 CaSiHx 中存在两种不同的氢物种。新相SrSiHx以包含倾斜[Sin]2链的相关结构结晶（a= 15.1051(5) Å,b= 3.95400(8) Å,c= 12.3431(3) Å，空间群Pnma）。 BaSiHxarea= 15.7(2) Å,b= 4.13(3) Å,c= 13.43(8); EuSiHxa= 15.17 Å,b= 3.95 Å,c= 11.56 Å (Z= 3)。
The binary metal silicides CaSi, BaSi, SrSi, and EuSi that crystallize in the CrB type absorb reversibly hydrogen. Hydrogen contents of the products were measured by the carrier gas hot extraction method (CaSiHx: 1.56 wt %,x≈︁ 1.06; SrSiHx: 1.35 wt %,x≈︁ 1.6; BaSiHx: 2.08 wt %,x≈︁ 3.4; EuSiHx: 0.99 wt %,x≈︁ 1.8). According to simultaneous thermogravimetric, DTA and mass‐spectroscopic analyses, the dehydrogenation for the different hydrides starts at 610 K for BaSiHx, at 675 K for CaSiHxand SrSiHx, and at 640 K for EuSiHx. BaSiHxreleases further hydrogen at 765 K and 1000 K, respectively, CaSiHxat 760 K. Fundamental morphological and structural changes caused by the hydrogenation of the silicides were detected and comprehensively characterized by SEM and X‐ray diffraction. According to XRD results, the crystal structures of the phasesMSiHx(M= Ca, Ba, Sr, Eu) are all orthorhombic (space groupPnma). The lattice parameters change froma= 4.559(1) Å,b= 10.731(1) Å,c= 3.890(1) Å (space groupCmcm,Z= 1) in CaSi toa= 14.4884(9) Å,b= 3.8247(1) Å,c= 11.2509(5) Å (Z= 3) in CaSiHxcaused by the hydrogen uptake that induces the formation of a threefold superstructure along theaaxis. In CaSiHx, the planes of the [Sin]2–zigzag chains are tilted and inter‐chain Si–Si contacts are formed formally corresponding to an oxidation to Si–. The hydrogen desorption process was investigated by in situ X‐ray diffraction studies which revealed the presence of two different hydrogen species in CaSiHx. The new phase SrSiHxcrystallizes in a related structure comprising tilted [Sin]2–chains (a= 15.1051(5) Å,b= 3.95400(8) Å,c= 12.3431(3) Å, space groupPnma). The lattice parameters of BaSiHxarea= 15.7(2) Å,b= 4.13(3) Å,c= 13.43(8); that of EuSiHxa= 15.17 Å,b= 3.95 Å,c= 11.56 Å (Z= 3).