The structure of a Frank-Kasper decagonal quasicrystal in the Zn-Mg-Dy system: comparison with the Al-Ni-Co system

摘要

The structure of a new decagonal quasicrystal in the Zn-Mg-Dy system has been studied by transmission electron microscopy and compared with that of a decagonal Al-Ni-Co (d-(Al-Ni-Co)) phase with primitive structure. Electron diffraction patterns of these two d phases reveal the same appearance of the Bragg reflections but with different unit lengths. The characteristic length, in and normal to the quasiperiodic plane, are a = 0.227 nm and c = 0.225 nm for d-(Zn-Mg-Dy), and a = 0.20 nm and c = 0.20 nm for d-(Al-Ni-Co); the c/a ratios are therefore also different. The local atomic arrangement of the d-(Zn-Mg-Dy) is proposed to be a tetrahedrally close-packed structure.