The presence and chemical nature of bulk vacancies in Al-Pd-Mn quasicrystals was identified by measuring the structure and composition of 2- and 5-fold cleavage surfaces of different pre-annealed quasicrystals subjected to post-cleavage heat treatments using scanning electron microscopy and Auger electron spectroscopy. A strong dependence of the surface structure from the pre-annealing was observed and explained by varying concentrations of bulk vacancies. The analysis of the data showed that as-grown Al-Pd-Mn quasicrystals contained Al, Pd, and Mn vacancies in supersaturated but near stoichiometric concentrations, while long-term pre-annealed samples contained a much lower vacancy concentration, with a tendency to have excess Al vacancies. It was found that Al and Mn vacancies were more mobile at lower temperatures than Pd vacancies, and that the diffusion of Mn vacancies was directly coupled to the mobility of Al vacancies. The results demonstrated that the evolution of the surface structure was primarily affected by bulk vacancies migrating toward the surface during heat treatments and provided a new methodology to characterize the vacancies in intermetallic alloys.

Surface Structure of Al-Pd-Mn Quasicrystals - Existence of Supersaturated Bulk Vacancy Concentrations. P.Ebert, M.Yurechko, F.Kluge, T.Cai, B.Grushko, P.A.Thiel, K.Urban: Physical Review B, 2003, 67[2], 024208 (8pp)