| Co-Investigator(Kenkyū-buntansha) |
MATSUO Susumu Nagoya University, School of Informatics and Sciences, Professor, 情報文化学部, 教授 (10023293)
ISHIMASA Tsutomu Hokkaido University, School of Engineering, Professor, 大学院・工学研究科, 教授 (10135270)
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| Research Abstract |
The main aim of this research is to study the quasicrysta phase stability of Al-Pd-Mn icosahedral phase. It have already been reported that an A1PdMn and the other icosahedral phases is not only an F-type icosahedral phase, but can be F2-type and F2M-type icosahedral phases. The experimental results of the diffuse scattering intensity are as follows.
1) The diffuse distribution of Al-Pd-Mu is elliptic spread toward the transverse direction, but that of Al-Cu-Fe is asymmetrical rhombic shape. 2) The diffuse scattering intensity distribution of Al-Pd-Mu is symmetrical along the longitudinal direction, but that of Al-Cu-Fe is asymmetric. The reason, called "asymmetrical" in this case, is that the center of the rhombus is not just on the diffraction point, but is located on the slightly inside. 3) The shape of diffuse intensity contour depends on the intensity. 4) The intensity of the diffuse scattering in Al-Cu-Fe depends little on the temperature below 300K.5) The diffuse intensity is pro
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portional to the nth power of the magnitude of q. The values of n range between -2 and -3.5 and depend on the direction and reflection.
Therefore, it is thought that the diffuse scattering is mainly produced by the defects. In the defects, a defect, called a (frozen) "phason" proper to a quasicrystal, is naturally included besides an impurity and/or defect included in a "usual" crystal. The experimental result seems to show the limit of elastic approximation as Huang scattering. The contour of the diffuse scattering intensity cannot individually be explained as every map of Huang scattering, and seems to consist of the sum of all three components.
As the comparison between experimental and calculation, we can think followings. The major defects in Al-Pd-Mu and Al-Cu-Fe can be exchange-type defects which are created by interchange of atoms and/or atomic clusters. However, the concentration of atoms and atomic clusters is unchanged from the ideal structure by this type of defect. Random phason is clearly classified into this type.
The type of a defect in the Al-Cu-Fe phase is similar to the exchange-type but is accompanied by deviation of concentration of atoms and atomic clusters from the ideal state. As the "asymmetrical" cannot be explained with the approximation of Huang scattering, it is probably caused by a size effect.
The major defects are exchange-type defects which are created by interchange of atoms and/or atomic clusters. And the concentration of atoms and atomic clusters is unchanged from the ideal structure by this type of defect. Random phason is clearly classified into this type. The results indicate presence of additional type of defect in the Al-Cu-Fe phase. The "asymmetrical" and the nth power dependence cannot be explained with the elastic approximation of Huang scattering. Less
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