Positron-Annihilation Study of Icosahedral AlPdMn Alloys

Abstract

We measured the positron-annihilation lifetime in A${\mathrm{l}}_{71.4}$P${\mathrm{d}}_{20.2}$M${\mathrm{n}}_{8.4}$, A${\mathrm{l}}_{71.9}$P${\mathrm{d}}_{19.7}$M${\mathrm{n}}_{8.4}$, A${\mathrm{l}}_{70.2}$P${\mathrm{d}}_{20.3}$M${\mathrm{n}}_{9.5}$, and A${\mathrm{l}}_{69.1}$P${\mathrm{d}}_{21.5}$M${\mathrm{n}}_{9.4}$ polyquasicrystalline icosahedral quasicrystals. As-grown and plastically deformed single quasicrystals of A${\mathrm{l}}_{70.6}$P${\mathrm{d}}_{21.1}$M${\mathrm{n}}_{8.3}$ were also studied. In every sample the lifetime spectrum consists of a single component with the lifetime of $206\ifmmode\pm\else\textpm\fi{}4\mathrm{ps}$. The results indicate that icosahedral quasicrystalline AlPdMn contains a dense distribution of vacancy-type sites. These trapping sites seem to remain unaltered during plastic deformation at high temperature.