Live Observation of the Growth of Quasicrystal Grains

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04-10-2004
Soon after their discovery in 1984, it was realised that quasicrystals (QC) constitute a new class of solids as they were found to differ both from crystals, because they lack periodicity, and from glasses, because they exhibit long-range order. Their particularities are noncrystallographic rotational symmetries, e.g. fivefold symmetry axes.

A challenge of quasicrystal science today is to understand the local rule of the growth of these very peculiar solids [1]. Thus one has to elucidate how the quasiperiodic order of these crystals can be extended to the size of single grains, routinely grown up to several centimeters.

Hence we performed the first in situ and real time observation of quasicrystal growth, using synchrotron X-ray radiography. A Bridgman furnace was combined with a diffractometer on the ID19 beamline.

With this live observation the growth and the evolution of the quasicrystal grains can be followed and provides the first unambiguous evidence of their facetted growth with the manifestations of steps. The facetted character is shared with crystalline complex metallic alloys. However it is very unusual for crystals of a single metallic element [2]. This facetted character of QC is therefore of paramount importance for future research.

Images of AlPdMn QC growing from the melt:

Figure 1: Al-Pd-Mn alloy of 30x7 mm2; thickness 700 µm. Images (pixel size 7.5 µm) of AlPdMn QC growing from the melt: (a) end of a growth sequence: pulling rate of the sample V = 0.4 µm/s, (b) V = 3.6 µm/s. Thermal gradient: G = 20 K/cm.

A movie of the quasicrystal growth is available:
quasicrystal_growth_movie.zip (11 mb).

References
[1] V.E. Dmitrienko, S.B. Astaf'ev, and M. Kléman, Phys. Rev. B, 59, 1 (1999).
[2] A.A. Chernov, Modern Crystallography 3, Springer, Berlin (1981).

Authors
T. Schenk (a), G. Reinhart (b), V. Cristiglio (c,a), J. Gastaldi (d), H. Klein (e), B. Grushko (f), H. Nguyen-Thi (b), N. Mangelinck-Noël (b), J. Härtwig (a), B. Billia (b) and J. Baruchel (a). 

(a) ESRF
(b) L2MP, UMR 6137, Université d' Aix-Marseille III (France)
(c) Università degli Studi di Torino, dipartimenti di fisica, Torino (Italy)  
(d) CRMCN, Marseille (France)
(e) Laboratoire de Cristallographie, Grenoble (France)
(f) IFF, Forschungszentrum Jülich GmbH (Germany)