Sektion Kristallographie

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AlCoNi quasicrystal sphere growth experiment from a metallic solution

Zeitschrift Fur Kristallographie 224(10): 471-477

Autoren/Herausgeber: Meisterernst G
Bauer B
Gille P
Erschienen: 2009

Crystal growth studies starting from spherical surfaces of single crystals can reveal morphological features that cannot be obtained in usual growth experiments. Especially, facets of a greater variety of crystallographic forms may occur that are otherwise hidden by the slowest growing faces which dominate the crystal's morphology. We did a sphere growth experiment with a decagonal Al72Co9Ni19 quasicrystal prepared from a large single-grain sample formerly grown using the Czochralski method from an off-stoichiometric melt. By heating the polished crystalline half-sphere to a temperature slightly higher than its own growth temperature a thin liquid layer of self-flux formed. A partial evaporation of Al being the solvent of this system caused re-crystallisation at the surface of the quasicrystalline sphere. After several times repeating this process at further increasing temperatures, tiny faces of four different crystallographic forms developed. By using an optical goniometer and electron scanning microscopy indexing of these facets was possible. With the only exception of the decagonal prism {10000} they had not been observed so far in contact to the melt. The results are discussed with respect to the inclined net plane concept established by Steurer and Cervellino [Acta Cryst. A57 (2001) 333-340]. The experimental approach is not specific to sphere growth studies of quasicrystals but can be applied to other high-temperature solution growth systems as well.

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