Positron annihilation spectroscopy was used to study atomic vacancies in quasicrystals. Structural vacancies, at concentrations of the order of 10-3, were observed in quasicrystals and approximants of the Al–Pd–Mn system. The first in situ measurements of the positron lifetime at high temperatures were performed, where the formation of thermal vacancies in Al70.2Pd21.3Mn8.5 could be observed directly. The annealing behavior of quenched-in vacancies, which coincided with data from earlier time-differential dilatometry studies after fast temperature changes, furnished vacancy migration properties and kinetics in quasicrystals. From measurements of the Doppler broadening of the positron-electron annihilation photon line at ambient temperatures, it was deduced that the vacancies observed in Al70.2Pd21.3Mn8.5 were located mainly in an Al-rich environment.

Atomic Vacancies in Quasicrystals - a Study by Positron Annihilation Spectroscopy. F.Baier, H.E.Schaefer: Journal of Alloys and Compounds, 2002, 342[1-2], 318-20