Estimation of neutron-irradiation-induced defect in 3C–SiC from change in XRD peak shift and DFT study

Neutron-irradiation-induced defects in 3C–SiC irradiated to 2.8–4.2 × 1026 n/m2 at 480–735 °C were investigated by XRD measurement, isochronal annealing and DFT calculation. The XRD peak shift revealed different features between the specimens irradiated at 480 °C and higher temperature than 585 °C. The peak shifts were larger at the higher angle in the specimen irradiated at 480 °C, while the specimens irradiated at higher temperature than 585 °C, amounts of their peak shifts were not simply related to the diffraction angles. Crystal lattice of the specimen irradiated at 480 °C was considered to expand isotropically due to the irradiation. On the other hand, that of the specimens irradiated at higher temperature than 585 °C would expand anisotropically. Modification of XRD profile by the formation of various kinds of point defects and their clusters in 3C–SiC was simulated using Rietveld method based on the DFT calculation results. Formation of the CC100 dumbbell complex defect expressed well the XRD peak shifts of 3C–SiC irradiated above 585 °C.