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.