The Influence of Temperature, Fluence, Dose Rate, and Helium Production on Defect Accumulation and Swelling in Silicon Carbide

Swelling and microstructure of silicon carbide (SiC) are studied by means of MeV-range ion irradiation. The material used is chemical vapor deposited high purity polycrystalline cubic (3C)-SiC. The swelling behavior is characterized by precision interferometric profilometry following ion bombardment to the diamond-finished surface over a molybdenum micro-mesh. Irradiation was carried out at temperatures up to 873 K, followed by profilometry at room temperature. Microstructural characterization by means of cross-sectional transmission electron microscopy has also been finished for selected materials. Irradiation induced swelling was increased with increasing the displacement damage level up to 0.3 dpa at all evaluated temperatures. At 333 K, the swelling was increased with increasing the damage level up to 1 dpa, and irradiation-induced amorphization was observed over 1.07 dpa. At the higher irradiation temperature, swelling was saturated over 0 3 dpa. The temperature dependence of saturated swelling obtained so far appeared very close to the neutron irradiation data. For the study of the synergism of displacement damage and helium production, a dual-beam experiment was performed up to 100 dpa at 873 K. Swelling of the dual-beam irradiated specimen was larger than that of single-beam irradiated specimen. The result also suggested the onset of unsteady swelling in high He/dpa conditions after "saturated point defect swelling" is once achieved at displacement damage levels over 50 dpa.