[en] Krypton ion irradiation of crystalline Ge and subsequent thermal annealing were both carried out with in situ transmission electron microscopy observations. The temperature dependence of the amorphization dose, effect of foil thickness, morphological changes during continuous irradiation of the amorphous state as well as the effect of implanted gas have been determined. The dose of 1.5 MeV Kr required for amorphization increases with increasing temperature. At a fixed temperature, the amorphization dose is higher for thicker regions of the specimen. Continuous irradiation of amorphous Ge at room temperature results in a high density of small cavities which grow with increasing dose. Cavities do not coalesce during growth but develop into irregular-shaped holes that eventually transform the amorphous Ge into a sponge-like material. Formation of the spongy structure is independent of Kr implantation. The crystallization temperature and the morphology of recrystallized Ge depend on the Kr⁺ dose. Voids are expelled from recrystallized Ge, while the sponge-like structure is retained after crystallization. (author)

[en] The temperature and pressure dependence of diffusion of Sn¹¹³ implanted in high-purity aluminium single crystals has been investigated by means of the serial sectioning technique. It was found that tin is a fast diffusing solute in Al. The activation volume of diffusion was found to be 0.87 ± 0.01 in atomic volume units at 787.5 K. (author)

[en] First, a review is given of defects created by low-temperature electron irradiation in the h.c.p. heavy lanthanides Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, in the double-h.c.p. light lanthanides Pr and Nd, and their light homologues Sc and Y. The wealth of the experimental data permits to establish general relationships between specific Frenkel-pair characteristics and crystallographic parameters, such as between the threshold energy for displacement, the interatomic distance and the c/a ratio. Another interesting empirical rule is the linear dependence of the interstitial migration temperature (normalized to the melting point) on the deviation of the c/a ratio from its ideal value which seem to have general validity for almost all h.c.p. metals, (Notable exceptions are Zn and Cd, with their extreme c/a ratios). A further result is the observation that the specific Frenkel-pair resistivity consists of two parts: a 'normal' phonon contribution and, in magnetic lanthanides, a contribution from spin scattering. Second, we treat a specific impurity, H, which forms solutions RH_x with several rare-earths up to relatively high values, for example x = 0.35 atoms of H per atom of Sc. The hydrogen atoms, which occupy tetrahedral interstitial sites in the h.c.p. unit cell, have a tendency to order at temperatures below 150-180 K, giving rise to resistivity anomalies and Snoek-like peaks in internal-friction spectra. A detailed analysis of the ordering using diffuse neutron scattering yields peculiar quasi-linear configurations of chains consisting of H-H pairs on second-neighbour tetrahedral sites along the c- axis surrounding a metal atom. (author)

[en] The effect of an internal stress on the formation of stacking fault tetrahedra is examined in a Cu-Fe alloy containing coherent γ-Fe particles. Localization of the formation of stacking fault tetrahedra was found around the γ-Fe particles. This is attributed to the development of vacancy-rich regions around them due to formation of inhomogeneously distributed interstitial clusters. Another example of a local stress effect examined is the formation of a linear array of stacking fault tetrahedra. It is shown that the strain field due to the pre-formed stacking fault tetrahedra brings about directional preference in the vacancy flow to induce such an alignment. (author)

[en] The lenticular bubbles produced by neutron irradiation in boron carbide are secondary defects which induce very high local stresses presenting the same dipolar character as those induced by dislocation loops. We have solved the problem of diffusion of point defects to lenticular bubbles by using an analytical calculation based on the effective-medium theory. The use of oblate spheroidal coordinates allowed us to replace the angular dependence of the elastic interaction energy, which produces the drift of point defects to the bubble, by a step function. Then a self-consistent calculation of the sink efficiency can be carried to the end and the respective effects of the stresses and of the randomness of the defect distribution can be separated. (author)

[en] Y₃Fe₅O₁₂ garnets have been irradiated by Mo and Xe ion beams at 2.3 and 3.3 GeV respectively. High-resolution electron microscopy (HREM), channelling Rutherford backscattering (RBS) and Moessbauer spectrometry have been used to determine the variation of the radius of latent damage tracks induced along the ion paths as a function of the electronic stopping powers between 34 and 56 MeV cm²mg^-1. On comparing the results obtained by different experimental methods it is found that the disorder characterized by channelling RBS measurements extends over the same cylindrical volume as the paramagnetic state observed by Moessbauer spectrometry. A direct HREM measurement of the radii shows a larger cylindrical volume than both the other measurements, indicating the existence of a distorted shell around the disordered core. (author)

[en] This paper describes a transmission electron microscopy (TEM) study of a body-centred-tetragonal metal (β tin) after room temperature implantation with 40 keV xenon ions. At low to medium doses, dark-field microscopy showed that a large fraction of the bubbles present (those with diameters less than 5 nm) contained solid xenon precipitates. From the inferred bubble pressures, it was demonstrated that these bubbles were in equilibrium, as expected from the high homologous implant temperature. At the highest dose, a large range of bubble sizes was found with strongly facetted bubbles having edge lengths in excess of 100 nm. Further results were obtained using a microscope cooling holder to follow the freezing of xenon in medium and large sized bubbles. The details of the gas adsorption on the bubble facets was deduced and the xenon content of the larger bubbles estimated. Of particular interest was that the xenon content of the larger bubble suggested that they were grossly underpressurized, in contrast with the coexisting small equilibrium bubbles. The bimodal nature of the bubbles is discussed using the critical radius concept within the framework of bias-driven cavity growth. (author)

[en] Chi-phase precipitation was observed by transmission-electron microscopy (TEM) in Mo-30 at.% Re and Mo-27 at.% Re specimens that had been irradiated with 1.8 MeV He ions at temperatures from 750degC to 1075degC. The precipitates formed at the rhenium-rich external surface and adopted both parallel and (111) twin orientations with respect to the matrix. Details of precipitate morphology and crystallographic orientation are reported. (author)

[en] Heavy-ion irradiation (14 MeV u^-1 Pb ions) of zircon crystals gives rise to linear latent tracks of 80 A diameter and length 140 μm. Direct observation of the track core, by high-voltage high-resolution electron microscopy at atomic resolution, reveals a core having roughly circular cross-section, with some facetting of the core/matrix interface on {101} planes of zircon. The core diameter appears quite uniform. Conventional transmission electron microscopy reveals an elastic strain field extending for a short distance into the zircon matrix. This appears to drop off more rapidly with distance, say 1/R², than do dislocation strain fields (∼ 1/R). Analysis of the various contrast mechanisms yields the result that the core is essentially amorphous. Our observations confirm directly the conclusions of previous authors, based on track etching and electrical conductivity measurements, that the irradiation damage is confined to a 50-100 A core region of atomically disordered material, with virtually no damage outside this region. Mechanisms for track production are discussed briefly, but it is concluded that the problem has not been fully appreciated by condensed matter physicists. In particular a damage confinement mechanism is required. Some tentative suggestions are proposed. (author)

[en] The recovery of the electrical resistivity is reported for low-temperature electron-irradiated cobalt and dilute Co-Si and Co-C alloys. Samples have been irradiated to a range of doses extending from 0.25 x 10 to 24.5 x 10²² m^-2. A large stage I recovery (up to 78%) with a number of substages has been observed. One of these substages (I_D2 at 53 K) is influenced by both irradiation dose and the impurity level; this stage can be attributed to correlated recovery. No evidence for a dose-dependent substage I_E is observed. The influence of silicon and carbon on the recovery is discussed. (author)