Formation of Decagonal Quasicrystal in the Al-Pd-Mn System and Its Structure

Abstract

Formation of a decagonal quasicrystal in Al 70 Pd 30- x Mn x alloys ( x =8-20) and its structure were examined by X-ray powder diffraction, electron diffraction and high-resolution electron microscopy. The decagonal quasicrystal is formed as a coexisting phase with an icosahedral phase in the composition range of x =10-15, and as a single phase at a composition of x about 20. The structure of the decagonal phase is a mixture of decagonal quasicrystalline regions with some linear phason strain and microcrystalline regions. We propose that the structure of Al-Pd-Mn decagonal quasicrystal may be interpreted as a tiling formed by atom cluster linkages, which are different to those reported in Al-Ni-Co and Al-Cu-Co decagonal quasicrystals.