Icosahedral quasicrystals in Zn-T-Sc (T=Mn, Fe, Co, Ni) alloys

TL;DR

This study discovers new icosahedral quasicrystals in Zn-T-Sc alloys with T=Mn, Fe, Co, Ni, highlighting the role of electron concentration and atomic ratios in their formation.

Contribution

It reports the synthesis and characterization of new primitive icosahedral quasicrystals in Zn-T-Sc alloys, expanding understanding of their structural and electronic properties.

Findings

New quasicrystals formed at specific alloy compositions

All quasicrystals share similar e/a ratios and structural parameters

Hume-Rothery mechanism influences quasicrystal formation

Abstract

Starting from the Zn17Sc3 cubic approximant, new quasicrystal alloys were searched by replacement of Zn with transition elements, T. In the cases of T=Mn, Fe, Co and Ni, new icosahedral quasicrystals are formed in as-cast alloys as major phases at the alloy compositions of Zn75T10Sc15. All these quasicrystals belong to a primitive type, and have 6-dimensional lattice parameters, a6D, ranging from 7.044 to 7.107 A. They have the valence electron concentrations, e/a, ranging from 2.01 to 2.14, and almost the same ratios between the edge-length of the Penrose tile, aR, and the averaged atomic diameter d: aR/d~1.75. Moreover other Zn- and Cd-based quasicrystals including the same type of atomic cluster, Tsai-type cluster, also have the same values of e/a~2.1 and aR/d~1.75. The equality in e/a indicates that the Hume-Rothery mechanism plays an important role for the formation of these quasicrystals.