TILING IN AL-PD-MN DECAGONAL QUASI-CRYSTAL, STUDIED BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

A decagonal phase which was grown from an icosahedral phase in a rapid ly solidified Al70Pd20Mn10 alloy by annealing at 800-degrees-C was exa mined by means of high-resolution electron microscopy. From the high-r esolution image, we directly determined a two-dimensional arrangement of atom clusters, which are structural units of the Al-Pd-Mn decagonal quasicrystal, in a wide region of about 100 x 100 nm2. The main part bf the observed area shows a highly ordered decagonal quasicrystal wit h weak linear phason strain. A tiling constructed by connecting the at om clusters with lines was compared with theoretical tilings.