Icosahedral quasicrystal and 1/1 cubic approximant in Au–Al–Yb alloys

Ishimasa, Tsutomu; Tanaka, Yuya; Kashimoto, Shiro

doi:10.1080/14786435.2011.608732

Cited by 78 publications

(100 citation statements)

References 34 publications

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“…The archetype Tsai-type i-YbCd 5.7 quasicrystal and related ternary quasicrystals 31 have been studied extensively. In particular, for i-YbCd 5.7 , the same Tsai-type clusters have been shown to comprise the backbone of the structure of the icosahedral phase with the same types of linkages, and full occupancy of the R icosahedron by Yb 2+ .…”

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confidence: 99%

Atomic structure of the i-R-Cd quasicrystals and consequences for magnetism

et al. 2016

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Atomic structure of the i-R-Cd quasicrystals and consequences for magnetism

et al. 2016

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“…In Au-Al-RE alloys, a metastable Tsai-type i-phase for RE = Yb has been reported, 10) whereas a stable i-phase has not yet been reported. Au 45 Al 40 Sc 15 i-phase is the first example of stable Tsai-type i-phase formed in Au-Al-RE alloys.…”

Section: Resultsmentioning

confidence: 99%

“…We examined a few possibilities of local atomic structure and chemical composition in the 1/1-phase based on the HAADF image, and found that the structure shown in Fig. 5 10) whereas Au/Al ratio of mixed sites in the model is slightly different from that in the Au 51 Al 35 Yb 14 . To confirm the validity of the model, a HAADF simulation was performed using the model, and the result is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Formation of an Icosahedral Quasicrystal and Its Approximant in Au-Al-Sc System

Kimoto²,

Edagawa

2015

Mater. Trans.

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The formation of the icosahedral (i-) and 1/1-approximant (1/1-) phases in the Au-Al-Sc system has been investigated. A primitive-type i-phase was found to form in an Au 45 Al 40 Sc 15 alloy. This i-phase was shown to be thermodynamically stable at 973 K. A stable 1/1-phase was found to form at 1173 K for compositions of Au 44+x Al 41¹x Sc 15 (x = 0, 1, 2, 3). High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) revealed that the 1/1-phase consists of Tsai-type icosahedral clusters. Similar local structures were observed in the HAADF-STEM image for the i-phase, indicating that the i-phase consists of Tsai-type clusters identical to the clusters in the 1/1-phase. The composition of the Au-Al-Sc i-phase is consistent with the formation conditions, including those in the valence electrons per atom ratio and in the atomic size factor, which has been shown previously for other Tsai-type i-phases. This fact demonstrates the importance of these conditions for stabilization of Tsai-type i-phases.

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“…Recently, new types of QC and AC have been discovered: 1 The Au-Al-Yb (AAY) QC exhibits unconventional quantum critical behavior as T → 0 and the AAY AC shows heavy Fermi liquid, 2 and the Au-GeYb (AGY) ACs show superconductivity below 1 K. 3 In this Short Note, we report a detailed structure analysis of the AGY(I) AC. For AGY(II), we are unable to provide a structure model owing to the lack of a single-phase sample.…”

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Crystal Structure of Superconducting 1/1 Cubic Au–Ge–Yb Approximant with Tsai-Type Cluster

et al. 2015

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We report the synthesis of a single-phase sample of the superconducting crystalline approximant Au64.0Ge22.0Yb14.0 and present a structure model refined by Rietveld analysis for X-ray diffraction data.Quasicrystals (QCs) are metallic alloys that possess long-range, quasi-periodic structures with diffraction symmetries forbidden to conventional crystals, while approximant crystals (ACs) are alloys whose composition is close to that of QCs and whose unit cell has atomic decorations similar to those of the QCs. In this Short Note, we report a detailed structure analysis of the AGY(I) AC. For AGY(II), we are unable to provide a structure model owing to the lack of a single-phase sample.Polycrystalline samples of the optimally compositioncontrolled compound Au 64.0 Ge 22.0 Yb 14.0 were synthesized, and their structures were characterized by powder X-ray diffraction using Cu Kα-radiation. Details of the sample preparation and X-ray diffraction analysis experiments were described in Refs. 3 and 1, respectively. Figure 1 shows a powder X-ray diffraction pattern of AGY(I), indicating the body-centered cubic structure (space group Im3) with a lattice parameter a = 1.4724(2) nm. The Rietveld analysis successfully converged with R-factors, R wp = 5.41%, R I = 0.95%, and R F = 0.59% (for the structure parameters, see Table I), assuming that the cluster center is occupied by an orientationally disordered tetrahedron. 4 This suggests that the alloy has a similar structure to the Tsaitype 1/1 AAY AC. This structure model contains 9 crystallographic sites and includes 174.1 atoms in total in a unit cell, which corresponds to the chemical * E-mail: deguchi@edu3.phys.nagoya-u.ac.jp Figure 2 shows the structure model for the AGY(I) AC. As shown in Fig. 2(a), the cluster center (M7 site) is occupied by Au atoms with an occupancy of 26.9%. The complicated shape of the cluster center, in which 4 atoms in total are ideally included, indicates an average of variously oriented tetrahedrons. The second shell [ Fig. 2(b)] is a dodecahedron, in which there are Au/Ge mixed sites named M2 and M4 sites. The third shell [ Fig. 2(c)] is an icosahedron, in which Yb ions exclusively occupy the Yb1 site. The icosahedron is surrounded by an icosidodecahedron [ Fig. 2(d)] in which the M1 and M6 sites are almost occupied by Au atoms and the M8 site is occupied by Ge with an occupancy of 95%. These shells, i.e., the dodecahedron, icosahedron, and icosidodecahedron compose the so-called Tsai-type cluster. Finally, Tsaitype clusters are embedded in the cage composed of M3 and M5 [ Fig. 2(e)]. The periodic arrangement of this cage 1

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Icosahedral quasicrystal and 1/1 cubic approximant in Au–Al–Yb alloys

Cited by 78 publications

References 34 publications

Atomic structure of the i-R-Cd quasicrystals and consequences for magnetism

Atomic structure of the i-R-Cd quasicrystals and consequences for magnetism

Formation of an Icosahedral Quasicrystal and Its Approximant in Au-Al-Sc System

Crystal Structure of Superconducting 1/1 Cubic Au–Ge–Yb Approximant with Tsai-Type Cluster

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