Solution growth of a binary icosahedral quasicrystal of ${\text{Sc}}_{12}{\text{Zn}}_{88}$

We report the discovery of a binary icosahedral phase in a Sc-Zn alloy obtained through solution-growth, producing millimeter-sized, facetted, single grain quasicrystals that exhibit different growth morphologies, pentagonal dodecahedra, and rhombic triacontahedra, under only marginally different growth conditions. These two morphologies manifest different degrees of quasicrystalline order. The discovery of $i{\text{-Sc}}_{12}{\text{Zn}}_{88}$ suggests that a re-examination of binary phase diagrams at compositions close to crystalline approximant structures may reveal other binary quasicrystalline phases.

Figure 1

(Color online) Growth morphologies of solution-grown $i{\text{-Sc}}_{12}{\text{Zn}}_{88}$. Panel (a) shows an example of the PD. Panel (b) shows a cluster of facetted grains displaying a RT morphology. The inset shows an isolated RT grain.

Figure 2

(Color online) Revised Sc-Zn phase diagram of reference. The Sc-Zn binary phase diagram taken from Ref. 12 is modified to include the quasicrystalline phase (labeled $\mathbf{Q}$). The inset presents the DSC data on the thermal decomposition of the quasicrystalline phase at $505°\text{C}$.

Figure 3

(Color online) Powder diffraction and high-energy x-ray diffraction from single grains of $i{\text{-Sc}}_{12}{\text{Zn}}_{88}$. Powder-diffraction pattern from powders of the PD facetted grains and RT facetted grains are shown in panels (a) and (b), respectively. Icosahedral indices using Elser’s notation (Ref. 13) are shown. Single grain high-energy x-ray diffraction patterns measured along the fivefold axis and twofold axes are shown in panels (c) and (e) for the PD grain and (d) and (f) for the RT sample. The lines in panel (e) indicate the twofold, threefold, and fivefold directions in the twofold scattering plane. The weak peak in the center of pentagon B in panel (c) is not observed in neighboring pentagon A since it does not originate in the fivefold plane, but slightly above it (within the range over which the sample is rocked).