Electron microscopy of quasicrystals and related structures

Abstract

Systematic electron microscopy of quasi crystals in an Al-14 at % Mn alloy has been carried out. High resolution imaging reveals fringes with spacings in the ratio of 1:τ. Besides 5-3-2 synnetry axes, other important zones of electron diffraction patterns are experimentally determined and compared with those generated by Landau grneration technique and by projection technique. It has been shown that the 'T' phase, which often co-exits with quasicrystal, is closely related to it and can be treated as a two dimensional quasiperiodic crystal stacked periodically along an icosahedral vector of a true quasi periodic incommensurate modulation in three, two and one dimensions. The quasi crystal, the 'T' phase and vacancy ordered τ phases and the respective real life examples of such modulations.