Positron annihilation studies of quasicrystals

Positron annihilation studies of various quasicrystalline alloys are reviewed. It is observed that both metastable and stable quasicrystalline alloy systems exhibit two-component positron lifetime spectra. The implications of these findings are discussed in the context of various structural models of the quasicrystalline phase, which is believed to be a new phase in condensed systems. We further observed that the two-component positron lifetime spectra change to single component spectra as the metastable quasicrystalline alloys transform to the crystalline phase, whereas the stable quasicrystalline alloys retain the two-component spectra even-after prolonged heat treatments.