A study was made of micro-defects and interfaces, in oxide films on FeAl or NiAl substrates, by using variable-energy positron lifetime spectroscopy. Di-vacancies, vacancy clusters and micro-voids were observed in the oxide scales. Their sizes and distributions were governed by the process which was used to synthesize the oxide film, and were influenced by the composition of the substrate. In the case of oxide/FeAl interfaces, the positron lifetimes were longer than those for the alumina layer itself; thus suggesting the existence of a greater defect concentration at such sites.

J.Xu, B.Somieski, L.D.Hulett, B.A.Pint, P.F.Tortorelli, R.Suzuki, T.Ohdaira: Applied Physics Letters, 1997, 71[21], 3165-7