Stable tenfold faceted single-grain decagonal quasicrystals of Al65Cu15Co20

Abstract

We report stable ${\mathrm{Al}}_{65}$ ${\mathrm{Cu}}_{15}$ ${\mathrm{Co}}_{20}$ decagonal quasicrystals which exhibit faceted columnar morphology. The column axis is along the tenfold direction, and it is faceted by the ten twofold planes. Faceted single grains, several millimeters in size were grown and characterized. Peritectic growth is fastest along the periodic tenfold axis and slowest along the nucleation controlled, quasiperiodic twofold directions. Single-crystal x-ray scattering verifies the two-dimensional quasiperiodic structure. The two-dimensional quasicrystalline structure is defect free on a length scale of 2000 Å and is layered with a thickness of 8.26 Å.