MATSUO Susumu Nagoya Univ., Grad.School of Info.Sci., Prof., 情報科学研究科, 教授 (10023293)
KASHIMOTO Shiro Hokkaido Univ., Grad.School of Eng., Inst, 大学院・工学研究科, 助手 (60329852)
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¥14,800,000 (Direct Cost : ¥14,800,000)
Fiscal Year 2004 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 2003 : ¥3,800,000 (Direct Cost : ¥3,800,000)
Fiscal Year 2002 : ¥9,600,000 (Direct Cost : ¥9,600,000)
Starting from Zn17Sc3-type approximant crystals, new icosahedral quasicrystals have been discovered in many Zn-based and Cu-based alloys : They are Zn-(Mg,Mn,Fe,Co,Ni,Cu,Pd,Ag,Pt,Au)-Sc, Zn-Mg-Yb and Cu-Ga-Mg-Sc. These new quasicrystals belong to P-type and have structural similarity to the Cd-based and the Ag-In-based quasicrystals. Among them Zn-(Mg,Fe,Co,Ni,Pd,Ag)-Sc and Cu-Ga-Mg-Sc, are thermodynamically stable and exhibit very high degree of structural perfection. All these quasicrystals, called Tsai-type in this report, have common properties as follows : The base metals are divalent or effectively divalent, namely Zn, Cd, Cu-Ga and Ag-In. They further include approximately 15 at.% of trivalent Sc or lanthanoid metals as well as divalent Ca or Yb. Addition of few percent of the third component has decisive role for stabilizing the quasicrystal structures except for the cases of binary stable quasicrystals, Cd-Yb and Cd-Ca. The substitution relationship in these quasicrystals indicates the important role of Hume-Rothery rule for the formation of Tsai-type quasicrystals.