Influence of growth kinetics and chemical composition on the shape of voids in quasi-crystals

We analyze the shape of internal voids in as-grown and long term annealed icosahedral Al–Pd–Mn quasi-crystals and distinguish growth and equilibrium shapes. From the growth shape we extract that the growth speed anisotropy is pronounced and changes with the chemical composition of the bulk material, favoring primarily the formation of fivefold oriented surfaces, while only small surface areas of three and even smaller twofold facets are observed. In contrast the equilibrium shape of voids exhibits no effect of the chemical composition of the bulk material. We show that the surface free energy exhibits only a very small anisotropy. This leads to richly faceted voids with much more types of facets as compared to voids determined by the growth kinetics.