Helium behavior in α-SiC ceramics investigated by NRA technique

The mechanisms involved in helium migration in α-SiC are investigated through the evolution of its microstructure and of the concentration profiles following annealing at 1300°C/30min for fluences of 1 and 5×10153Hecm−2 and a He implantation energy of 500keV. Helium profiling is performed using the 3He(d,α)1H NRA technique with an improved detection limit of 5atppm. The NRA and TEM techniques clearly show that depending on the initial fluence, a proportion of the helium is trapped within the grain and a part of the helium is released. Analysis of the helium profile changes after annealing enabled to determine a value of the volume diffusion coefficient close to (8±1)×10−17m2s−1 for both fluences studied.