Icosahedral AlCuFe quasicrystals, which have a unique atomic structure and unusual physical properties, are of considerable interest in materials science. Studying their behavior under high pressure is an important task that allows us to understand the stability of the quasicrystalline phase and identify possible phase transitions.
This paper presents the results of an X-ray structural study of an icosahedral AlCuFe quasicrystal, conducted under high pressure conditions reaching several megabars. The experiments were carried out using a high-pressure chamber with diamond anvils and synchrotron radiation. An analysis of the diffraction patterns made it possible to determine changes in the lattice parameters of the quasicrystal under pressure.
The obtained data indicate compression of the AlCuFe structure with increasing pressure. Anisotropic compression along various crystallographic directions is observed. At certain pressure values, signs of a phase transition accompanied by a change in the diffraction pattern were detected. Further analysis of the high-pressure phase structure will allow us to establish its atomic structure and determine the mechanism of the phase transition.
The in situ synchrotron X-ray diffraction study of icosahedral (i)-AlCuFe quasicrystal (QC) under high pressure up to 104 GPa at room temperature using a diamond anvil cell is presented. No significant changes in the diffraction pattern were found within the pressure range. Five characteristic peaks of i-AlCuFe QC are preserved up to 104 GPa. The unit cell volume of i-AlCuFe QC decreases monotonically up to 72 GPa. The experimental compression curve P–V below 72 GPa is approximated by the Birch-Murnaghan equation of state with V0=2023(19) Å3, K0=131(7) GPa, K’=4.0 (fixed). The obtained parameters of the equation of state are consistent with the previous studies. In the range of 72–75 GPa, a volume change is observed, indicating a phase transition from i-AlCuFe QC to an approximating crystal (AC) with a similar local arrangement of atoms. i-AlCuFe QC retains the structure up to 72 GPa, then passes into AC with a small displacement of atoms.
The first natural quasicrystal, icosahedrite (Al63Cu24Fe13), was discovered in the Khatyrka meteorite in 2009, opening up a new field in Earth and planetary sciences. The discovery of natural QC changed the understanding of traditional QCs, previously obtained only in laboratories. A second quasicrystal, decagonal (Al71Ni24Fe5), was found in the same meteorite. The contact of these quasicrystals with stishovite indicates their formation under ultra-high pressure. It is assumed that the Khatyrka meteorite formed 4.5 billion years ago and experienced a pressure of at least 5 GPa and a temperature of 1200 °C.
The results of the study contribute to the understanding of the stability and behavior of quasicrystals under extreme conditions and can be used to develop new materials with unique properties.
Author: Sota Takagi, Atsushi Kyono, Saki Mitani, Neo Sugano, Yuki Nakamoto, Naohisa Hirao
Institute: Department of Earth Evolutionary Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan, Center for Science and Technology in Extreme Environments, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan, Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan