AlCuFe quasicrystals with a unique aperiodic structure are of considerable interest in materials science. This paper is devoted to the study of the atomic structure of the AlCuFe quasicrystal by neutron diffraction using the double isotope substitution technique. The use of different isotopes allows one to vary the contrast between the alloy components, which increases the accuracy of determining the partial radial distribution functions (PRDF).
AlCuFe samples were synthesized by arc melting followed by annealing to achieve a high degree of quasicrystalline ordering. Diffraction experiments were carried out on a high-resolution diffractometer with a stationary neutron source. The obtained diffraction patterns were analyzed using structural information extraction software.
Neutron diffraction experiments using double isotopic substitution involving two isotopes Fe and Cu were performed on six samples of quasicrystalline AlCuFe with 6D face-centered icosahedral symmetry. From the obtained data, heteroatomic and homoatomic pair correlation functions were calculated for the given structure. The analysis shows the presence of a localized copper site at the center of the 6-dimensional solid, which allows to obtain a clear, although general, idea of the structure. In this 6D NaCl-type structure, iron, copper and aluminum are chemically ordered and occupy successive concentric “shells” on large atomic surfaces centered on two main atomic positions: n1 = [0, 0, 0, 0, 0, 0] and n2 = [1, 0, 0, 0, 0, 0] (indexed with respect to the primitive unit cell). There is reason to believe that some of the aluminum forms a mixture with iron or is contained in a small volume within the iron surface.
The results showed that Al and Cu occupy certain positions in the icosahedral lattice, and Fe is predominantly located in the centers of clusters. The obtained PFRRs made it possible to establish interatomic distances and coordination numbers for different pairs of elements. The data analysis indicates the presence of chemical short-range order in the AlCuFe quasicrystal, which is important for understanding its physical properties.
Author: M CornierQuiquandon, R Bellissent, Y Calvayrac, JW Cahn, D Gratias, B Mozer
Institute: Materials Science and Engineering Laboratory, NIST, Gaithersburg, MD 20899, USA, Leon Brillouin Laboratory (CEA-CNRS), CE Saclay, F-91191 Gif-sur-Yvette, France, CECM/CNRS, 15 rue G. Urbain, F-94407 Vitry Cedex, France