On the growth of decagonal Al-Ni-Co quasicrystals from the ternary melt

Abstract

Abstract High-quality, single-Frain samples of decagonal Al-Ni-Co quasicrystals with volumes of up to 0.8 cm3 and an approximate composition of Al72Ni11 Co17 have been grown from the ternary melt. The precise growth methods and conditions are discussed in detail. X-ray diffraction patterns of crushed single grains and of single-grain samples are exceptionally sharp indicating a high degree of structural order with no evidence of second phases. Transmission electron micrographs also reveal sharp diffraction patterns in the even n layers but diffuse scattering in the odd n layers, indicative of a structure intermediate between the Al73Co27 and Al69Ni31 end members. The electrical resistivity measured directly from cut bars for currents flowing perpendicular to the crystalline direction (i.e. perpendicular to the c axis) is non-metallic, with a broad maximum around 180 K, and a value of approximately 310 μω cm at 300 K. The resistivity for currents flowing parallel to the c axis is metallic and is almost an order of magnitude smaller in value than for i ⊢ c.