Luo ZP, Hashimoto H
Okayama University of Science, Japan.
Micron. 2000 Oct;31(5):487-92. doi: 10.1016/s0968-4328(99)00128-6.
A new ordered structure W' with a lattice parameter (a = 2.05 nm) about three times as large as that of the fundamental face-centered cubic W phase (a = 0.6848 nm) has been found in the Mg-Zn-Y system by means of transmission electron microscopy. The W' and W phases have the cube-to-cube orientation relationship. Moreover, the strong electron diffraction spots of the W' phase showed pseudoicosahedral symmetry, implying that it is a crystalline approximant of the Mg-Zn-Y icosahedral quasicrystal. In the high-resolution electron microscopic images of the W' phase, Penrose tiles of pentagons and boats with an edge length of a(p) = 0.481 nm can be identified. A binary tile of crown subunit has also been deduced from such a tiling. Translation domains of the W' phase have also been observed and the translation vectors at the domain boundary are: a(p), tau x a(p) and (1 + tau) x a(p), respectively, where (1 + tau) x a(p) equals to the edge length a(r) of the big obtuse rhombus of the W' phase and tau = (1 + square root of 5)/2, is the golden ratio.
通过透射电子显微镜在Mg-Zn-Y体系中发现了一种新的有序结构W'，其晶格参数（a = 2.05 nm）约为基本面心立方W相（a = 0.6848 nm）的三倍。W'相和W相具有立方对立方的取向关系。此外，W'相的强电子衍射斑点显示出准二十面体对称性，这意味着它是Mg-Zn-Y二十面体准晶体的晶体近似物。在W'相的高分辨率电子显微镜图像中，可以识别出边长为a(p) = 0.481 nm的五边形和船形彭罗斯瓷砖。还从这种平铺中推导出了冠亚基的二元瓷砖。也观察到了W'相的平移畴，畴边界处的平移矢量分别为：a(p)、τ×a(p)和(1 + τ)×a(p)，其中(1 + τ)×a(p)等于W'相大钝角菱形的边长a(r)，τ = (1 + √5)/2，即黄金比例。
