Positron annihilation lifetimes of the stable icosahedral (i) Al-Pd-Mn quasicrystal and its (1/1, 2/1)-AlPdMnSi and 1/0-Al12Re approximant crystals were measured at ambient temperature. The observed single-lifetime of the i-Al-Pd-Mn quasicrystal was very close to that of the (1/1, 2/1)-AlPdMnSi approximant crystals, indicating that the same type of structural vacancies exists in all these specimens. On the other hand, the lifetime of 1/0-Al12Re approximant crystal, which has no structural vacancies, was significantly shorter than the above results. The relationship between the positron lifetimes and mean valence-electron density was considered.

Structural Vacancies in Al-Pd-Mn Quasicrystal and its (1/1, 2/1)-AlPdMnSi Approximant Crystals - Positron Lifetime Studies. Y.Takagiwa, J.T.Okada, K.Kimura, H.Kitahata, Y.Matsushita, I.Kanazawa: Philosophical Magazine, 2008, 88[13], 1929-34