TWINNING IN THE STRUCTURE OF THE DECAGONAL PHASE AL65CU20CO15

The existence of twinning in the pseudo-decagonal phase Al65Cu20Co15 has been established through TEM studies. From electron diffraction patterns, a rhombic crystalline lattice with a very large unit cell is easily identified. Diffraction patterns for microtwinned regions exhibit splitting and distortion of the reflections which is a result of the overlap of lattices which are rotated by 36-degrees with respect to one another. While patterns from single components of the twins exhibit only pseudo-tenfold symmetry, those from the microtwinned regions exhibit nearly perfect tenfold symmetry.