Formation of Tsai-type 1/1 approximants in In-Pd-RE (RE: rare earth metal) alloys

Abstract

The formation of the 1/1 crystal approximant phase (1/1 phase) to the icosahedral phase (i phase) in In-Pd-RE (RE: rare earth metal) systems has been investigated. A new series of 1/1 phases were found in In₅₃Pd₃₃RE₁₄ (RE; Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm) alloys. For Y, Sm, Gd, Tb, Dy, and Ho, the 1/1 phases were found in annealed alloys, indicating that they are thermodynamically stable. The atomic structure of the 1/1 phases was directly observed by high-angle annular dark-field imaging performed via scanning transmission electron microscopy, revealing that the 1/1 phases consisted of a periodic arrangement of Tsai-type icosahedral clusters. Further, the atomic size effect on i phase formation, as well as formation conditions previously reported for other Tsai-type i and 1/1 phases were examined. It was found that the ratio of the atomic radius of base metals such as In and Pd affects i phase formation. Moreover, the appropriate range of the radius ratio for i phase formation was narrower than that for 1/1 phase formation.

Keywords:

• icosahedral quasicrystal
• crystal approximant
• In-Pd-(rare earth metal) alloy

Acknowledgement

The authors would like to thank T. Hiroto of Tokyo University of Science (TUS) for his help in the single-roller melt spinning experiments and T. Hara of National Institute for Materials Science for his help in the SEM-EDS experiments.

Notes

Present address: Department of Materials Science and Engineering, Akita University, Tegata Gakuen-machi, Akita-shi, Akita 010-8502, Japan

Additional information

Funding

Funding. This work was financially supported by a Grant-in-Aid for Scientific Research on Priority Areas “Nano Materials Science for Atomic Scale Modification 474” from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.