Verlag des Forschungszentrums Jülich
JUEL-1650
Schönfeld, B.
Untersuchung von Frenkeldefekten in tieftemperaturbestrahlten HCP Kristallen mit Hilfe der diffusen Röntgenstreuung
88 S., 1980
Abstract
Single crystals of 3 hexagonal metals (Zn, Cd, Mg) were irra-
19 - 2 diated at 4.5K with 3MeV electrons up to doses of ~10 e Icm •
The irradiation induced defects were investigated by measurements
of the Huang diffuse scattering of X-rays, the lattice
parameter change and the electrical resistivity change. Only
for Zn a random distribution of single interstitial atoms (S.I.A.)
and vacancies was found. The S.I.A. was characterized by a large
relaxation volume of (3.• 6±0.7) atomic volumes and a strong
anisotropy of the defect displacement field. Consistent with a
dumbbell configuration of the S.I.A. the large displacement was
along the c-axis. The contribution of a Frenkel defect to the
electrical resistivity change was PF= (15.3±5.7) ~ncm/at%. For
Cd interstitial agglomerates of <10 interstitials were found.
Their size increased with the irradiation dose. This indicated
interstitial mobility at the irradiation temperature. For Mg
interstitial agglomerates of 2-3 interstitials were observed.
It was shown, that these agglomerates were formed by interstitial
migration during irradiation, similar to Cd. In contrast
to Cd, no dose dependence of their size was found. This unique
behaviour was tentatively explained by the existence of a nucleation
barrier. During thermal annealing in stage II small interstitial
agglomerates of ~10 interstitials were found for all 3
metals. In the case of Zn and Cd (cia %1.85) they seem to nucleate
and grow on the basal plane, in the case of Mg (cia ~1.6) however,
on prismatic planes.
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