Strain profiles in ion implanted ceramic polycrystals: An approach based on reciprocal-space crystal selection

Abstract

The determination of the state of strain in implanted materials is a key issue in the study of their mechanical stability. Whereas this question is relatively easily solved in the case of single crystals, it remains a challenging task in the case of polycrystalline materials. In this paper, we take benefit of the intense and parallel beams provided by third generation synchrotron sources combined with a two-dimensional detection system to analyze individual grains in polycrystals, hence obtaining "single crystal-like" data. The feasibility of the approach is demonstrated with implanted UO 2 polycrystals where the in-depth strain profile is extracted for individual grains using numerical simulations of the diffracted signal. The influence of the implantation dose is precisely analyzed for several diffracting planes and grains. It is shown that, at low fluences, the development of strain is mainly

Strain relaxation in He implanted UO2 polycrystals under thermal treatment: An in situ XRD study

“…As shown in Figure 1, the maximal damage values are 0.5 and 0.2 dpa for 60 keV 4 He and 500 keV 3 He ions respectively. Note that the thickness of the damaged layer (which is quite close to the strained one [20]) is about 0.3 µm for 60 keV He implantations but much larger for 500 keV He ion implantation.…”

“…X-ray diffraction measurements were performed on BM32 beamline (ESRF, Grenoble) using a parallel highly monochromatic (E/E≈10 -4 ) X-ray beam in the /2 geometry. These data collections were performed in single grains [20] of the X11 as-implanted He 500 keV polycrystal using a 17 keV X-ray beam and a point detector (see Table 1 and section 2.c.iii for detailed sample description). Grains with four different orientations ({111}, {200}, {220}, {311}) have been probed.…”

“…Using this methodology, it is possible to derive a swelling in the implanted layer that is equivalent to that measured on samples doped with short lived α-emitters [19]. Secondly in case of implantation using high energy He ions, the strain profile may not be constant over depth [20]. Finally, the chosen analytical technique has to enable a measurement of strains over the entire implanted layer.…”

“…Moreover these studies are performed on UO 2 polycrystals implanted with two kinds of He ions: either 60 keV 4 He or 500 keV 3 He ions. The first ion energy offers the possibility to work on implanted layers with a well-defined mechanical behavior at room temperature and which present a simple in-depth strain profile [17] [20] [18]. The second ion energy has been chosen to enable a direct comparison of strain relaxation kinetics with He release kinetics [5] [6].…”

Mechanical behaviour near grain boundaries of He-implanted UO2 ceramic polycrystals

“…where s/3 denotes the linear free swelling, which can vary with the implantation depth z [13,14]. This swelling loads mechanically the sample surface, producing stress and strain fields.…”