A channelling study of vacancy-solute complexes in Al-0.04 at.% Sn

Vacancy trapping at tin atoms during the recovery of a fast-quenched dilute aluminium-tin alloy and its effect on the isomer shift of the119Sn Mossbauer isotope

“…Figure 4 shows the interstitial-tin-vacancy complexes suggested experimentally (figures 4(a), 4(b) and 4(e)) [8] and theoretically (figures 4(c) and ( d ) ) [39]. It is very probable that in tin-monovacancy pairs substantial tin relaxation does not occur [8].…”

“…Figure 4 shows the interstitial-tin-vacancy complexes suggested experimentally (figures 4(a), 4(b) and 4(e)) [8] and theoretically (figures 4(c) and ( d ) ) [39]. It is very probable that in tin-monovacancy pairs substantial tin relaxation does not occur [8]. In this case the displacement of the tin atom towards the vacancy does not lead to energy gain but rather to energy increase, as the tin atom moves against the potential barrier set up by the four common nearest neighbours with the vacancy on the {1,1,0} plane.…”

“…Based on the analysis of the positron lifetime spectra and the corresponding initial vacancy distribution after the quench, on the structure of the Mossbauer spectra, i.e. line positions and widths, and on the tin relaxation observed in ion-channelling experiments [6][7][8]381, we assign both peaks appearing in the Mossbauer spectra to tinvacancy associates. First, the resonance line at 2.275 mm sel was ascribed to tin atoms with perfect atomic surroundings, tin-vacancy pairs and to those tin-defect associates where the relaxation does not increase the effective free volume around the tin atom substantially.…”

“…In conclusion, based on the structure of the Mossbauer spectra, on the line positions and widths, on the high vacancy concentration found by positron lifetime measurements and on the tin relaxation observed in ion-channelling experiments [6][7][8]381, we propose that the Mossbauer line at 2.275 mm s-l, besides substitutional tin with perfect surroundings, corresponds to tin-vacancy pairs and to those relaxed interstitial-tin-vacancy complexes or generally tin-defect complexes where the relaxation does not result in a substantial increase of the effective volume available for the tin atom. Hence tin atoms along dislocations, collapsed vacancy loops and larger dislocation loops may well give a contribution to this line.…”

“…They observedrelaxation of tin atoms to{ 1,1, l} planes (tetrahedral and octahedral interstitial positions) upon annealing at 220 K in irradiated [ 6 8 ] and Sn-implanted [38] samples. They proposed the interpretation that, by the trapping of vacancies migrating at 220 K [8] and produced during implantation [38], vacancy clusters are formed at tin atoms, and if their geometry is favourable the tin atoms relax towards the centre of the vacancy clusters, namely to the nearest interstitial positions. In this way tin-trivacancy , tin-tetravacancy and tin-hexavacancy clusters are formed (figures 4(a), (b) and (e)).…”