Vacancy effects on the formation of He and Kr cavities in 3C-SiC irradiated and annealed at elevated temperatures

Abstract

Polycrystalline 3C-SiC was sequentially irradiated at 400 and 750˚C with 120 keV He 2+ and 4 MeV Kr 15+ ions to 10 17 and 410 16 cm-2 , respectively. The Kr 15+ ions penetrated the entire depth region of the He 2+ ion implantation. Three areas of He 2+ , Kr 15+ and He 2+ + Kr 15+ ion implanted SiC were created through masked overlapping irradiation. The sample was subsequently annealed at 1600˚C in vacuum and characterized using cross-sectional transmission electron microscopy and energy-dispersive x-ray spectroscopy. Compared to the He 2+ ion only implanted SiC, He cavities show a smaller size and higher density in the co-implanted SiC. At 25 dpa, presence of He in the co-implanted 3C-SiC significantly promotes cavity growth; much smaller voids are formed in the Kr 15+ ion only irradiated SiC at the same dose. In addition, local Kr migration and trapping at cavities occurs, but long-range Kr diffusion in SiC is not observed up to 1600˚C.

The effects of helium, strontium, and silver triple ions implanted into SiC

“…11 (a) and TEM, STEM and EDX results, Ag is the most trapped species in the cavities. Similar trapping of Ag by He cavities has been reported in Ag and He co-implanted into SiC at room temperature then annealed at 1100 °C for 5 h [ 12 ] while Sr trapping was also reported in the Sr and He co-implanted SiC annealed at 1000 °C for 5 h [ 24 ]. The lack of or insignificant trapping of Sr by cavities in the present study might be due to unavailability of empty cavities as they are already occupied by Ag precipitates as seen in Fig.…”

“…To fully understand the migration behaviour of different fission products (FPs) in SiC, their migration needs to be investigated in environments mimicking the nuclear environment i.e., where FPs coexist in the presence of helium at elevated temperatures. Limited work has been done on the role of helium in the migration of FPs surrogates such as Ag, Fe, Mg, Kr, and Sr, implanted into SiC [ 12 , [22] , [23] , [24] , [25] ]. However, no work has been reported on the influence of helium in the migration of FPs co-implanted into SiC.…”

Damage microstructure evolution of helium ion irradiated SiC under fusion relevant temperatures

“…Thus, understanding the behaviour of He in SiC under fusion-relevant conditions (He-appm, DPA and irradiation temperature) is pertinent. There have been numerous studies into the effect of radiation damage on SiC with neutrons [7]- [11], heavy ions [9], [12] and light ions [3], [13]- [23]. However, work performed at fusion relevant temperatures (>1000°C) often consists of complex irradiation and experimental schedules, either with post-irradiation annealing or with ex-situ dual and triple ion-beam irradiations [15], [23], [24] making it difficult to determine the underlying atomistic behaviour of He.…”

Observations of He platelets during He ion irradiation in 3C SiC

“…Heavier ion irradiations have not resulted in platelet formation although bubbles have still been observed. Krypton bubbles have been seen after 4 MeV Kr irradiation after annealing to 1600 o C [42], and Xe bubbles have also been observed in 3C SiC crystals after 800 keV Xe ion irradiation at room temperature [43]. Although all common SiC polytypes (3C, 4H and 6H) are promising candidates for nuclear materials ( [44][7] [45]), 3C SiC has a greater resistance to thermal shock than 4H or 6H [6], an important property in the case of LOCAs in a fission reactor [6], and for plasma striking the PFM in a fusion reactor arising from plasma instabilities [46].…”