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 Al70.3Pd20.6Mn9.1 icosa hedral quasicrystal (IQC) by means of x-ray diffraction topography (Lang's method). One possible direction of the apparent Burger vectors of loop-shap ed defects (LSDs) was determined to be B = [110101] by the invisibility cri terion, whose physical component is parallel to the two-fold axis 1/ tau [1 /0, 1/1, 0/1] of the IQC. Apart from the relaxation of strain fields around the faceted dodecahedral holes and lamellar precipitates, LSDs may well or iginate from the growth of the quasicrystal, which shows that these defects could be a kind of intrinsic defect in the quasicrystals.