The microcrystalline state of slowly solidified decaprismatic Al-Co-Cu(-Si) needles

Abstract We show that samples of the decagonal Al-Co-Cu(-Si) phase produced by different slow solidification methods are in the microcrystalline and not in the quasicrystalline state. Parameters for the underlying unit cell are a = b ≈ 51.3 Å, c ≈ 4.1 Å and γ = 108°. Experiments on differently produced samples show the same microcrystalline state and that the (5,7) approximant seems to be highly favoured, compared with the set of possible high-order approximant states.