Regensburg 2002 – wissenschaftliches Programm

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M: Metallphysik

M 10: Quasikristalle III

M 10.6: Fachvortrag

Dienstag, 12. März 2002, 15:45–16:00, H6

Kinetics of thermal vacancies in AlPdMn-quasicrystals — •F. Baier, K. Sato, and H.-E. Schaefer — Univ. Stuttgart, Inst. f. Theo. und Angew. Physik

For studying atomic vacancies in quasicrystals the specific techniques of positron annihilation spectroscopy has been employed. In quasicrystals and approximants of the AlPdMn- and in the ZnMgHo-systems structural vacancies in the concentration range of 10⁻³ have been observed [1,2,3]. We perform the first in-situ measurements of the positron lifetime at high temperatures, where the formation of thermal vacancies in i-Al_70.2Pd_20.3Mn_8.5 can be observed directly [4]. The annealing behavior of quenched-in vacancies, which coincide with the data from earlier time-differential dilatometry studies after fast temperature changes [1], gives access to the vacancy migration properties and kinetics in quasicrystals. From the coincident measurement of the Doppler broadening of the positron-electron annihilation photon line at ambient temperatures we deduce that the vacancies observed in i-Al_70.2Pd_20.3Mn_8.5 are predominantely located in an Al-rich environment. Supported by the DFG SPQK SCHA428/22-1,2,3,4.

[1] F. Baier et al., Mat. Sci. Eng. A 294-296 (2000) 650.

[2] F. Baier et al., Mat. Sci. For. 363-365 (2001) 179.

[3] K. Sato e. al., Phys. Rev. B 59 (1999) 6712.

[4] F. Baier et al.,to be published.