A metastable icosahedral quasicrystal in the Zn–Mg–Yb alloy system

Abstract

The formation conditions for a Zn–Mg–Yb icosahedral quasicrystal, which is primitive (P) type and has a six-dimensional lattice parameter a _6D = 7.371 Å, have been studied. This quasicrystal is formed only by quenching from a temperature higher than 650°C in the narrow composition region between approximately Zn₇₆Mg₉Yb₁₅ and Zn₇₁Mg₁₇Yb₁₂. On annealing, this quasicrystal transforms to the Zn₁₇Yb₃-type cubic phase and the hexagonal Z phase, both of which are equilibrium phases in this alloy system. An annealing experiment, a morphological study of these phases and differential thermal analysis have revealed that this quasicrystal is a metastable phase.

Acknowledgement

This work was partly supported by the 21COE program ‘Topological science and technology’ from the Ministry of Education, Culture, Sport, Science and Technology of Japan.