Long-range and short-range F-type ordering in Zn–Mg–Ho icosahedral phase

The behavior of the F-type superlattice in the Zn–Mg–Ho icosahedral phase was studied with respect to long-range ordering and short-range ordering. At the composition Zn60Mg30Ho10, a gradual decrease in intensities of superlattice reflections was observed in the alloys annealed at high temperatures, i.e. at 544, 549, 559 and 563°C. This observation indicated that the long-range order parameters decrease in the high temperature region. The disordered icosahedral phase formed in Zn60Mg35Ho5 alloy exhibits circular diffuse scattering related to F-type ordering. Electron microscopy revealed that the diffuse scattering is caused by domains with approximate size of 100 Å, which are related according to an anti-phase relationship.