Discovery of a New Binary Icosahedral Quasicrystal: Sc12Zn88
An extensive study of the phase diagram of ScZn alloys provided a real surprise during solution growth at the Ames Laboratory. Millimeter-sized, facetted, single grains with unconventional morphologies: pentagonal dodecahedra and rhombic triacontahedra were discovered.
High-energy x-ray diffraction on station 6ID-D was employed to confirm the exciting discovery of a new binary icosahedral quasicrystal, i-Sc12Zn88. Complete reciprocal space planes were recorded using an area detector and rocking the sample through small angular ranges about axes perpendicular to the incident beam along the five-fold and two-fold axes, respectively. The enhanced penetration depth of 129-keV x-rays ensured that the sample bulk was probed. The icosahedral symmetry group and the high perfection of the structure were satisfactorily shown for the entire grain.
The discovery of i-Sc12Zn88 is exciting because it isonly the second example of a stable binary icosahedral quasicrystal known to date.