The Structure of an Al-Ni-Co Decagonal Quasicrystal Studied by Atomic-Scale Electron Microscopic Observations

The structure of an Al–Ni–Co decagonal phase, which was found as a highly-ordered decagonal quasicrystal in an Al72Ni20Co8 alloy, has been studied by atomic-scale observations of high-resolution electron microscopy (HREM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). It has been found that a large columnar cluster of atoms with a decagonal section of about 3.2 nm in diameter exists as a basic structural unit. A structural model of the cluster is proposed from HREM and HAADF-STEM images.