Preliminary Characterization of Loop-Shaped Defect in the AlPdMn Icosahedral Quasicrystal by Conventional X-Ray Topography

Loop-shaped contrasts were observed in the as-grown Al_70.3Pd_20.6Mn_9.1 icosahedral quasicrystal (IQC) by means of x-ray diffraction topography (Lang's method). One possible direction of the apparent Burger vectors of loop-shaped defects (LSDs) was determined to be B = 1ī0ī01 by the invisibility criterion, whose physical component is parallel to the two-fold axis 1/τī/0, 1/1, 0/ī of the IQC. Apart from the relaxation of strain fields around the faceted dodecahedral holes and lamellar precipitates, LSDs may well originate from the growth of the quasicrystal, which shows that these defects could be a kind of intrinsic defect in the quasicrystals.