Highly ordered structure of icosahedral quasicrystals in Zn-Mg-RE (RE ≡ rare earth metals) systems

Abstract A new group of stable icosahedral phases (i-phases) in the Zn-Mg-RE system were found to have an ideal composition close to Zn50 Mg42RE8 (RE ≡ Y, Gd, Tb, Dy, Ho or Er). The new i-phases exhibit a highly ordered and nearly perfect face-centred icosahedral lattice as revealed by electron and X-ray diffraction and high-resolution electron microscopy. Powder X-ray diffraction indicates that the i-phase has long-range structural order with a correlation length over 1000 Å, which is the largest found in the Frank-Kasper group. These new i-phases have the common valence concentration (about 2.08) and could be regarded as a new class of Hume-Rothery alloys.