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 is 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-Al 12Re approximant crystal, which has no structural vacancies, is significantly shorter than the above results. We discuss the relationship between the positron lifetimes and mean valence-electron density.
- Positron annihilation