Positron-Annihilation Studies of Frank-Kasper-Type Quasicrystals of the Mg–Zn–Ga–Al and the Mg–Zn–Rare-Earth System
Positron-Annihilation Studies of Frank-Kasper-Type Quasicrystals of the Mg–Zn–Ga–Al and the Mg–Zn–Rare-Earth System
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Mg-Zn-Ga-Al 和 Mg-Zn-稀土系 Frank-Kasper 型准晶的正电子湮没研究
DOI：
10.1143/jjap.40.259
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发表时间：
2001
影响因子：
1.5
通讯作者：
S. Takeuchi
中科院分区：
文献类型：
--
作者：
E. Hamada;Kiminori Sato;Yasufumi Takahashi;H. Uchiyama;I. Kanazawa;N. Oshima;Takenori Suzuki;M. Nakata;Tomoyoshi Yoshida;S. Takeuchi
我们对Frank-Kasper（F-K）型二十面体准晶、Mg-Zn-Ga-Al的2/1和1/1近似晶体以及Mg-Zn-RE（RE=稀土金属Y、Ho和Gd）合金的稳定F-K型二十面体准晶进行了正电子湮没实验。结果表明，在Mg-Zn-Ga-Al的二十面体相和近似相中都存在高密度的三十面体团簇空位。此外，在本研究中，我们报告了一个非常有趣的发现，稳定的非铝基准晶，如二十面体准晶Mg-Zn-RE系统也包含高密度的结构空位，类似于稳定的铝基准晶。特别地，实验估计二十面体准晶Mg_（34）Zn_（58）Y_8和Mg_（40）Zn_（52）Ho_8的结构空位密度分别为3 ×1020和4 ×1020 cm ~（-3）。这些结果为Mg-Zn-RE稳定二十面体准晶的结构模拟提供了重要信息，这是二十面体准晶的一个新的研究课题。
We have performed positron-annihilation experiments for a Frank-Kasper (F-K)-type icosahedral quasicrystal, 2/1 and 1/1 approximant crystals of Mg–Zn–Ga–Al, and the stable F-K-type icosahedral quasicrystals of Mg–Zn–RE (RE=rare-earth metal, Y, Ho and Gd) alloys. It is shown that a high density of vacant centers in triacontahedral clusters exists in both icosahedral and approximant phases of Mg–Zn–Ga–Al. Furthermore, in the present study, we report a very interesting finding that stable non-Al-based quasicrystals such as the icosahedral quasicrystal Mg–Zn–RE system also contain a high density of structural vacancies, similar to the stable Al-based quasicrystals. In particular, it is estimated experimentally that the structural vacancy densities for icosahedral quasicrystal Mg34Zn58Y8 and Mg40Zn52Ho8 are 3 ×1020 and 4 ×1020 cm-3, respectively. These results provide important information on the structural modeling of the stable icosahedral quasicrystal Mg–Zn–RE, which is a recent research topic of the icosahedral quasicrystals.