Formation of a decagonal quasicrystalline film by reactive diffusion in Al/Co multilayers

Abstract

The formation of a decagonal Al-Co quasicrystalline film by reactive diffusion in a multilayer material and its thermal stability are studied. From experimental results obtained by differential scanning calorimetry, in situ ramped resistance measurements, X-ray diffraction and transmission electron microscopy, it is shown that Al/Co multilayers corresponding to an Al/Co ratio of 13/4 transform through heat treatment into a single-phase decagonal structure. Two reaction steps, which correspond to the transformation of the film into a monoclinic structure of the Al9 Co2 type, precede the formation of the quasicrystalline state observed at about 500oC. Once formed, the quasicrystalline film is stable upon annealing from room temperature up to 710oC. Above this temperature, it transforms into periodic structures of the monoclinic Al13 Co4 and orthorhombic Al3 Co (or Al11 Co4 ) types.