Positron-annihilation studies of rhombic triacontahedral-type icosahedral quasicrystals and their 1/1 and 2/1 approximants in the Al-Mg-Zn alloy system
Positron-annihilation studies of rhombic triacontahedral-type icosahedral quasicrystals and their 1/1 and 2/1 approximants in the Al-Mg-Zn alloy system
复制标题
Al-Mg-Zn合金系菱形三十面体型二十面体准晶及其1/1和2/1近似体的正电子湮没研究
DOI：
10.1103/physrevb.64.024202
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发表时间：
2001
影响因子：
3.7
通讯作者：
U. Mizutani
中科院分区：
文献类型：
--
作者：
Kiminori Sato;H. Uchiyama;Y. Takahashi;I. Kanazawa;R. Suzuki;T. Ohdaira;T. Takeuchi;T. Mizuno;U. Mizutani
用正电子湮没寿命测量、正电子湮没寿命测量和多普勒展宽技术，系统地研究了Al-Mg-Zn合金系中的菱形三面体型二十面体准晶及其1/1和2/1类准晶。我们可以成功地推导出该合金系统的结构空位密度。结构空位密度分别为∼4.56×10−3、4.82×10−3和5.05×10−3。此外，还研究了正电子的运动。计算了含二十面体准晶的合金体系的平均正电子扩散长度、正电子在基质中的平均扩散长度、正电子扩散系数和正电子迁移率。1/1准晶的正电子扩散系数(∼1.79cm2 S−1)基本相同，但2/1准晶的正电子扩散系数下降到1.61×10−1 cm2 S−1和二十面体准晶的1.44×10−1 cm2 S−1。这第一次实验估计是通过将正电子湮没寿命测量与使用慢正电子束的正电子湮没多普勒展宽测量很好地结合起来进行的。结果表明，随着近似值阶数的增加，基质中的热解正电子趋于局域化。
Rhombic triacontahedral-type icosahedral quasicrystal and its 1/1 and 2/1 approximants in Al-Mg-Zn alloy system were systematically studied by means of positron-annihilation lifetime measurements and positron-annihilation lifetime and Doppler-broadening measurements using the slow-positron-beam technique. We could successfully derive the structural vacancy density in this alloy system. The structural vacancy densities were∼ 4.56× 10− 3 for the 1/1 approximants, 4.82× 10− 3 for the 1/2 approximant, and 5.05× 10− 3 for the icosahedral quasicrystal. In addition, the positron motions were investigated. The average positron-diffusion length, average positron-diffusion length in matrix, positron-diffusion coefficient, and positron mobility in this alloy system including the icosahedral quasicrystal were estimated. The positron-diffusion coefficients for the 1/1 approximants were almost identical (∼ 1.79 cm 2 s− 1) to each other, but decrease down to 1.61× 10− 1 cm 2 s− 1 for the 2/1 approximant and 1.44× 10− 1 cm 2 s− 1 for the icosahedral quasicrystal. This first experimental estimation was performed by coupling the positron-annihilation lifetime measurements to the positron-annihilation Doppler-broadening measurements using the slow-positron beam excellently. The results indicated that the thermarized positrons in matrix tend to localize as the order of the approximant increases.