ACTA

Tsai-Type Quasicrystal and Its Approximant in Au-Al-Tm Alloys

K. Tanaka^a, Y. Tanaka^a, T. Ishimasa^a, M. Nakayama^b, S. Matsukawa^b, K. Deguchi^b and N.K. Sato^b
^aDivision of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
^bDepartment of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan

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A P-type icosahedral quasicrystal with a six-dimensional lattice parameter a_6D = 7.411 Å is formed as an equilibrium phase in Au-Al-Tm alloy, of which composition was analyzed to be Au₄₆Al₃₈Tm₁₆ by electron probe microanalysis. This quasicrystal is observed as a predominant phase in both as-cast and Au₄₉Al₃₄Tm₁₇ alloys annealed at 910°C, and as one of main phases in the alloy slowly cooled from 1020°C. A 1/1 approximant, Au₄₈Al₃₈Tm₁₄, is also formed near the composition of the quasicrystal. This is a body-centered cubic structure (space group: Im3̅) with a lattice parameter a = 14.458 Å that is an isostructure to the recently reported 1/1 Tsai-type approximant in Au-Al-Yb. This approximant is characterized by disorderly arranged four Au-Al atoms centered at the Tsai-type cluster, presence of atoms at 8c site, and chemical ordering of Au and Al at sites forming a partial triacontahedron.

DOI: 10.12693/APhysPolA.126.603
PACS numbers: 61.66.Dk, 61.44.Br