Positron-trapping mechanism at grain boundaries.

Abstract

Positron trapping at grain boundaries has been observed in fine-grained samples of Zn--0.123 wt. % Al--0.063 wt. % Mg by positron-lifetime measurements. Positron trapping at precipitates was also found. The temperature dependence of the positron-trapping rate shows that the positron-trapping mechanism at grain boundaries and precipitates is diffusion controlled, where the positron diffusion constant is proportional to ${T}^{\mathrm{\ensuremath{-}}1/2}$. No evidence of detrapping is observed in this alloy.