Dislocations in basic-nickel decagonal Al-Ni-Co single quasicrystals

摘要

We present a study of dislocations in decagonal Al_(70)Ni_(21)Co_9 quasicrystals by means of diffraction contrast analysis as well as convergent-beam electron diffraction in the transmission electron microscope. The nickel-rich Al-Ni-Co quasicrystals show diffraction patterns characteristic of the basic-nickel decagonal phase exhibiting almost no diffuse scattering. We succeeded in growing this phase in the form of large single quasicrystals. The two-beam bright-field images show a homogeneous background and no striation contrast as reported for other Al-Ni-Co decagonal phases. We have, for the first time in a two-dimensional quasicrystal, observed the weak contrast-extinction condition.