A novel technique for measuring diffusivities of short-lived radioisotopes in solids

Abstract

Abstract After reminding the reader of the major techniques for measuring diffusion coefficients in solids, a detailed description of the conventional radiotracer techniques is presented. These allow to measure solid-state diffusivities in the regime 10– 8–10– 24 m2s– 1 and therefore, and for other reasons to be discussed, are superior to all competing methods. However, the conventional radiotracer techniques suffer from the restriction that they are not applicable to radio-tracer atoms with half-lives t 1/2 ≲ 1 d. The main objective of this paper is to introduce a novel experimental set-up which enables us to perform radiotracer-type diffusivity measurements with short-lived radioisotopes (1 d ≳ t ≳ 10 min). First results on the diffusion of 31Si (t 1/2 = 2.6 h) and 11C (t 1/2 = 20.38 min) in Si–Ge alloys and Si –C–N-based ceramics measured in this set-up are presented.