The techniques of positron annihilation spectroscopy and time-differential dilatometry were used to study atomic vacancies. In the quasicrystals and approximants studied here,

structural vacancies could be observed at ambient temperatures; with atomic concentrations above 10-4. Via in situ measurements of the positron lifetime and time-differential dilatation in i-Al70.2Pd21.3Mn8.5 following rapid temperature changes at high temperatures, the formation and migration of thermal vacancies could be observed. It was also demonstrated that the chemical environment of structural vacancies in i-Al70.2Pd21.3Mn8.5 at ambient temperatures was dominated by Al atoms. This was reflected by the characteristic core electron momentum distribution as monitored by coincident Doppler broadening studies of the positron-electron annihilation photon line.

Atomic Vacancies in Quasicrystals - Positron Annihilation Spectroscopy and Time-Differential Dilatometry. F.Baier, H.E.Schaefer: Physical Review B, 2002, 66[6], 064208 (6pp)