Structure solution of the Al69.2Cu20Cr10.8 ϕ phase. Issue 1 (10th January 2022)

• Record Type: Journal Article
• Authors: Samuha, Shmuel; Tamari, Rimon; Grushko, Benjamin; Meshi, Louisa
• Is Part Of: Journal of applied crystallography. Volume 55:Issue 1(2022)
• Page Start: 74
• Page End: 79
• Publication Date: 2022-01-10
• Subjects: intermetallics -- Rietveld refinement -- strong‐reflections approach -- electron crystallography -- structure prediction; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576721011961
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : The atomic model of a new ϕ phase of Au–Cu–Cr was determined using powder X‐ray diffraction and verified by similarity to the known ζ phase. The similarity was assessed using a `strong‐reflections approach' based on analysis of electron diffraction patterns. Abstract : The stable ϕ phase that forms below ∼923 K around the Al69.2 Cu20.0 Cr10.8 composition was found to be hexagonal [ P 63, a = 11.045 (2), c = 12.688 (2) Å] and isostructural to the earlier reported Al6.2 Cu2 Re X phase [Samuha, Grushko & Meshi (2016). J. Alloys Compd. 670, 18–24]. Using the structural model of the latter, a successful Rietveld refinement of the XRD data for Al69.5 Cu20.0 Cr10.5 was performed. Both ϕ and X were found to be structurally related to the Al72.6 Cu11.0 Cr16.4 ζ phase [ P 63 / m, a = 17.714, c = 12.591 Å; Sugiyama, Saito & Hiraga (2002). J. Alloys Compd. 342, 148–152], with a close lattice parameter c and a τ‐times‐larger lattice parameter a (τ is the golden mean). The structural relationship between ζ and ϕ was established on the basis of the similarity of their layered structures and common features. Additionally, the strong‐reflections approach was successfully applied for the modeling of the ϕ phase based on the structural model of the ζ phase. The latter and the experimental structural model (retrieved following Rietveld refinement) were found to be essentially identical.