Interpretation of some Yb-based valence-fluctuating crystals as approximants to a dodecagonal quasicrystal

• Published in: Philosophical magazine (Abingdon, England) Vol. 98; no. 22; pp. 2018 - 2034
• Main Authors: Ishimasa, Tsutomu, Mihalkovič, Marek, Deguchi, Kazuhiko, Sato, Noriaki K., de Boissieu, Marc
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 03.08.2018
• Subjects: Approximant; Condensed Matter; dodecagonal; Materials Science; Physics; quasicrystal; valence-fluctuation; Yb-based
• ISSN: 1478-6435; 1478-6443; 1478-6433
• DOI: 10.1080/14786435.2018.1470339

The hexagonal ZrNiAl-type (space group: P 2m) and the tetragonal Mo 2 FeB 2 -type (space group: P4/mbm) structures, which are formed in the same Yb-based alloys and exhibit physical properties related to valence-fluctuation, can be regarded as approximants of a hypothetical dodecagonal quasicrystal. Using Pd-Sn-Yb system as an example, a model of quasicrystal structure has been constructed, of which five-dimensional crystal (space group: P12/mmm, a DD  = 5.66 Å and c = 3.72 Å) consists of four types of acceptance regions located at the following crystallographic sites; Yb [0 0 0 0 0], Pd[1/3 0 1/3 0 1/2], Pd[1/3 1/3 1/3 1/3 0] and Sn[1/2 00 1/2 1/2]. In the three-dimensional space, the quasicrystal is composed of three types of columns, of which c-projections correspond to a square, an equilateral triangle and a three-fold hexagon. They are fragments of two known crystals, the hexagonal α-YbPdSn and the tetragonal Yb 2 Pd 2 Sn structures. The model of the hypothetical quasicrystal may be applicable as a platform to treat in a unified manner the heavy fermion properties in the two types of Yb-based crystals.