Positron lifetime spectroscopy, and shape analysis of the Doppler-broadened positron annihilation peak, were performed on samples which contained 28, 40 or 50at%Al. The electronic structure of the open-volume defects, which were probably double vacancies according to the positron spectroscopic data, was independent of the heat treatment. Slight increases in the average positron lifetime, as a function of quenching temperature, indicated double-vacancy densities which were sufficiently high to cause the positron wave-function to overlap with more than one defect. The positron lifetimes which corresponded to the trapping of vacancy-type defects increased with the Al content. Changes in the shape of the annihilation peak suggested that the addition of Al caused a chemical shift of the 3d electrons of Fe to lower momenta.

Defects in Iron Aluminides Probed with Positrons. B.Somieski, J.H.Schneibel, L.D.Hulett: Philosophical Magazine Letters, 1999, 79[3], 115-23