Unique Shapes of Micro-Pits Formed in an Al–Pd–Mn Icosahedral Quasicrystal by Anodic Etching

抄録

The shapes of micro-pits formed in an Al–Pd–Mn icosahedral quasicrystal have been examined by alternating sequence of electrochemical etching and scanning electron microscopy (SEM) observations. Anodic etching was executed on fivefold and twofold surfaces of the single-quasicrystal. Prolonged anodic etching in a solution of CH₃OH+HNO₃ (volume ratio 3 : 1) followed by SEM observations has revealed that two different types of micro-pits, i.e. pre-existing micro-voids and electrochemical etch-pits, develop into the same regular shape. The micro-pits develop into a pentagonal pyramid on the fivefold surface, and a flat-bottomed rhombic pyramid on the twofold surface. It is shown that these two polyhedral etch-figures correspond to two different sections of a regular rhombic triacontahedron.