Quasicrystal-crystal interfaces in bulk materials

The formation of interfaces of simple crystals with icosahedral quasicrystals has been described. Crystals take on various orientation relationships (ORs) with the quasicrystals in order to make low energy interfaces by matching close packed planes across the interfaces. In the icosahedral phase the closest packed planes are fivefold and twofold. Among various possibilities, an OR will get selected by the surface on which nucleation of a phase occurs. Since one of the phases is quasicrystalline and the other is crystalline, even within the same OR there are variations of several degrees. The high symmetry of the icosahedral phase ensures many possible orientations for planar matching with another phase. The quasiperiodicity ensures an epitaxy with periodic planes of many possible spacings at the interface. Epitaxy can be observed as coincidence of spots in the reciprocal space and verified by imaging in high resolution electron microscopy. In this article examples of interfaces of Al-Cu-Fe icosahedral phases with lead, bismuth and tin, and Mg-Zn-Y icosahedral phases with magnesium are shown. The high symmetry of the icosahedral phase ensures that epitaxy is produced on nearly all interfaces in bulk. Slight misorientations across interfaces are accommodated by dislocations.