Structural studies of monoclinic approximants of Al13Fe4 and τ2-inflated Al13Co4 by the high-angle annular dark-field method
Structural studies of monoclinic approximants of Al13Fe4 and τ2-inflated Al13Co4 by the high-angle annular dark-field method
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高角度环形暗场法研究 Al13Fe4 和 τ2 膨胀 Al13Co4 的单斜晶近似结构
DOI：
10.1093/oxfordjournals.jmicro.a023656
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
A. Tsai
中科院分区：
文献类型：
--
作者：
K. Saitoh;T. Yokosawa;Michiyoshi Tanaka;A. Tsai
我们拍摄了两个单斜晶系Al13Fe4的高角环形暗场像，晶格参数分别为a=1.5489 nm，b=0.80831 nm，c=1.2476 nm和β=1.2476°。8：43-48)及其τ2膨胀的Al13Co4，晶胞参数为a=3.984 nm，b=0.8148 nm，c=3.223 nm，β=107.97°(马先锋，L，郭克华(1994年)，冶金材料学报25A：47-56)。用会聚束电子衍射法测定了τ_2Al_(13)Co_4近似物的空间群为P_2/m。我们发现，单斜晶系Al13Fe4和τ_2膨胀的Al13Co4由相同的五方原子团簇的基本结构组成，其边长为0.47 nm。我们还发现，在Al-Ni-Fe、Al-Cu-Co、Al-Co和Al-Ni-Co等十方准晶中，τ_2-Al_(13)Co_4中存在直径为2 nm的五重原子团。参照单斜晶系Al_(13)Fe_4的结构，在会聚束电子衍射对称性HAADF图像的基础上，建立了τ_2膨胀Al_(13)Co_4的结构模型。通过常规的高分辨电子显微镜图像和仿真对模型进行了验证。比较了Al-Ni-Fe、Al-Cu-Co、Al-Co和Al-Ni-Co十方准晶中τ2Al13Co4的2 nm团簇和直径为2 nm的5倍原子团簇。
We have taken high-angle annular dark-field (HAADF) images of two monoclinic approximants, Al13Fe4with lattice parameters ofa= 1.5489 nm,b= 0.80831 nm,c= 1.2476 nm and β = 107.72° (Black P J (1955),Acta Crystallogr. 8: 43–48) and its τ2-inflated Al13Co4with lattice parameters ofa= 3.984 nm,b= 0.8148 nm,c= 3.223 nm and β = 107.97° (Ma X L and Kuo K H (1994),Metallurgical Materials Transactions25A: 47–56). The space group of the τ2Al13Co4approximant has been determined to be P2/m using the convergent-beam electron diffraction method. We have found that the monoclinic Al13Fe4and τ2-inflated Al13Co4approximants are composed of the same basic structure of a pentagonal atom cluster with an edge length of 0.47 nm. We have also found that a fivefold atom-cluster with a 2 nm diameter exists in τ2-Al13Co4, which was observed in decagonal quasicrystals of Al-Ni-Fe, Al-Cu-Co, Al-Co and Al-Ni-Co by conventional high-resolution electron microscopy (HREM). A structural model of τ2-inflated Al13Co4is constructed on the basis of the convergent-beam electron diffraction symmetry HAADF images by referring to the structure of monoclinic Al13Fe4. The model is examined by the conventional HREM images and simulations. The 2 nm cluster of τ2Al13Co4is compared with the fivefold atom-cluster with a 2 nm diameter in decagonal quasicrystals of Al-Ni-Fe, Al-Cu-Co, Al-Co and Al-Ni-Co.