Studies of Phason Dynamics in Quasicrystal by Mechanical Spectroscopy
| Project/Area Number |
16560581
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | Tokyo University of Science |
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Principal Investigator |
TAKEUCHI Shin Tokyo University of Science, Dept.of Mater.Sci., 基礎工学部, 教授 (60013512)
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| Co-Investigator(Kenkyū-buntansha) |
TAMURA Ryuji Tokyo University of Science, Dept.of Mater.Sci., 基礎工学部, 助手 (50307708)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2004: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Keywords | quasicrystal / icosahedral phase / mechanical spectroscopy / internal friction / phason dynamics / メカニカルスペクトル |
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| Research Abstract |
In quasicrystals, there exist phason degrees of freedom and an application of a stress on quaiscrystal results in relaxation of the stress due to phonon-phason coupling. The purpose of the present investigation is to detect the stress relaxation in single icosahedral quasicrystals by means of the mechanical spectroscopy technique and to obtain information of the phason dynamic in the quasicrystal. Single icosahedral quasicrystalline bars having a two-fold symmetry axis have been cut out from a single quasicrystal of Al-Pd-Mn grown by the Bridgman method. The internal friction of the specimens has been measured by use of the Dynamical Mechanical Analyzer in the bending mode at high temperatures from the room temperature to 900K. The heating rate was 5K/min and the measured frequencies were 0.1, 1, 10 and 100Hz.
The results have shown that a large relaxation peak with the peak internal friction value of tan δ≒0.1 has been observed at about 850K. From the frequency dependence of the peak, we have obtained the activation enthalpy of the relaxation as 5〜6eV and the pre-exponential factor as 10^<-26〜33>s. The peak width was about three times as large as that of the single Debye peak. The large activation enthalpy and the extremely small pre-exponential factor compared with the single atomic jump time of the order of 10^<-14>s indicate that the relaxation is not a simple atomic relaxation but a complex relaxation, i.e., the relaxation is interpreted to be due to a phason relaxation resulting from independent collective jumps of plural number of atoms. Referring to the minimal model of the internal friction in icosahedral quasicrystal by Rochal and Loman (Phys.Rev.B 66 (2002) 144204), it is concluded from the large value of the internal friction peak that the phonon-phason coupling constant is of the same order as the phason elastic constant.
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Report
(3 results)
Research Products
(13 results)
