Measurements were made of positron annihilation lifetime spectra in Al-Pd-Re alloys (table 2), of positron annihilation Doppler-broadening spectra for slow variable mono-energetic positron beams in Al70.7Pd2l.34Re7.96 and Al71.5Pd20.3Mn8.2, and of positron annihilation lifetime spectra for slow positron beams in Al71.5Pd20.3Mn8.2. The results indicated that every sample contained a dense distribution of vacancy-type sites. This was consistent with predictions of the relationship between the presence of vacant centers in clusters and the stability of icosahedral quasi-crystals. The structural vacancy densities in icosahedral quasi-crystals of Al70.7Pd2l.34Re7.96 and Al71.5Pd20.3Mn8.2 were estimated to be 7.7 x 1020 and 5.0 x 1020/cm3, respectively.

Positron-Annihilation Studies of Stable Al-Based Icosahedral Quasicrystals. K.Sato, Y.Takahashi, H.Uchiyama, L.Kanazawa, R.Tamura, K.Kimura, F.Komori, R.Suzuki, T.Ohdaira, S.Takeuchi: Physical Review B, 1999, 59[10], 6712-6

Table 2

Positron Lifetimes in Al-Pd-Re Alloys