Approximant-based orientation determination of quasicrystals using electron backscatter diffraction

Grzegorz Cios,Gert Nolze,Aimo Winkelmann,Tomasz Tokarski,Ralf Hielscher,Radoslaw Strzałka,Ireneusz Bugański,Janusz Wolny,Piotr Bała

doi:10.1016/j.ultramic.2020.113093

Abstract

Orientation mapping of quasicrystalline materials is demonstrated using crystalline approximant structures in the technique of electron backscatter diffraction (EBSD). The approximant-based orientations are symmetrised according to the rotational point group of the quasicrystal, including the visualization of orientation maps using proper colour keys for quasicrystal symmetries. Alternatively, approximant-based orientation data can also be treated using pseudosymmetry post-processing options in the EBSD system software, which enables basic grain size estimations. Approximant-based orientation analyses are demonstrated for icosahedral and decagonal quasicrystals.

Highlights

Since the discovery of a “metallic phase with long-range orienta tional order and no translational symmetry” in 1982 [1], quasicrystals (QC) [2] remain an extremely fascinating topic in materials science [3]
For phases with a quasicrystal symmetry M/m m m (M = 8, 10, 12) and the respective enantiomorphic group M 2 2, the assignment of a quasicrystal orientation from an approximant orientation is possible based on the general discussion of Euler angles in [53]
A given orientation derived within the point group of the approximant is related to a correspondingly higher number of orientation de scriptions which are symmetry-equivalent in the point group of the quasicrystal

Summary

Introduction

Since the discovery of a “metallic phase with long-range orienta tional order and no translational symmetry” in 1982 [1], quasicrystals (QC) [2] remain an extremely fascinating topic in materials science [3]. The crystal structure of a quasicrystal is characterised by a nonperiodic arrangement of atoms, which no longer complies with threedimensional translation symmetry as a prerequisite of the classical space-group types [15]. It can become a challenge to char acterise quasicrystalline materials if the available analysis methods do not allow for quasicrystal symmetry. This includes common crystallographic techniques in materials science, such as electron backscatter diffraction (EBSD) [16,17] or transmission

Methods

Results

Conclusion