Damage and annealing behavior in neutron-irradiated SiC used as a post-irradiation temperature monitor

• SiC crystal was used as an irradiation temperature monitor in a thermal reactor. • The irradiation temperature is overestimated by an electrical measurement of SiC. • Annealing-induced elimination of C i accounts for the electrical changes in SiC. • Hardness of SiC increases with neutron irradiation and then decreases by annealing. Chemical vapor deposited polycrystalline SiC was irradiated with neutrons in a thermal reactor at nominal 550 ℃ to 2 × 10 19 n/cm 2 (E > 0.1 MeV). Isochronal annealing of the irradiated SiC was performed to determine the sample irradiation temperature, which is based on the annealing temperature dependence of the sample electrical resistivity. The estimated irradiation temperature of 615 ℃ is significantly higher than the target temperature recorded by thermocouple. The Raman spectroscopy results indicate that the C-C bonds formed in the irradiated SiC are preferentially annealed out than Si-Si bonds. The behavior is attributed to the fast migration and elimination of interstitial C during annealing, which accounts for the annealing-induced electrical resistivity changes in SiC. The hardness of SiC characterized by nanoindentation is found to increase with neutron irradiation and decrease after post-irradiation annealing, which is associated with the production and recovery of radiation defects in SiC.