ELECTRON-BEAM IRRADIATION EFFECTS IN AL-NI-CO DECAGONAL QUASI-CRYSTAL

By observing the change of the diffraction pattern and the lattice image, structural changes by electron beam irradiation have been investigated for Al-Ni-Co ordered decagonal quasicrystal, which was recently identified by the present authors. By 100 kV electron beam irradiation, essentially no change was detected in the diffraction pattern even after half an hour exposure to the electron beam. On the other hand, by 300 kV irradiation, drastic changes were observed after only a few minutes of irradiation; in the diffraction pattern the diffraction spots became diffuse and all the ordered spots and weak main spots disappeared; in the lattice image, the characteristic ring contrast in the decagonal phase became indistinct. However, no reconstruction of the ring pattern was recognized, suggesting that the phason strains, if introduced, are limited to components of wavelength shorter than the inter-ring distances (approximately 2 nm).