Mössbauer effect study of interstitial atom trapping sites around57Co impurities in tungsten

Abstract The impurity interstitial interactions in diluteW57 Co alloys during 3 MeV electron irradiation at 80 K and subsequent isochronal annealing have been studied using Mossbauer technique and electrical resistivity measurements. During 80 K irradiation, the population of one57Co impurity single interstitial complex, two different trapping sites for di-interstitials and three57Co impurity interstitial cluster complexes could be identified by the appearance of six additional absorption lines in the Mossbauer spectra with isomer shifts of +0.72 to +0.41 mm/s relative to the substitutional line and quadrupol splittings ranging from 1.89 to 0.17 mm/s. The trapping behaviour ofW57 Co could be described by a nucleation trap model using a trapping radius ratioro/rv . = 0.25 (57Co atom without captured interstitial/vacancy) and assuming an increase of the trapping radius per trapped interstitial ΔLr = r 0. Comparing the Mossbauer data and the resistivity data, we found that on an average only about 23% of the...