Irradiation response of liquid-phase sintered SiC assisted with Y2O3-Al2O3 sintering additive at 300°C up to 100 dpa

Abstract

Sintering additive, typically Y2O3-Al2O3 mixed powder, is usually added in the liquid-phase sintering (LPS) of nuclear-grade SiC ceramics to lower the sintering temperature, and therefore the effect of the Y2O3-Al2O3 sintering additive on the irradiation response, especially the irradiation swelling of the LPS-SiC materials, must be carefully investigated. A comparative study of chemical vapor deposited (CVD) SiC and LPS-SiC on their irradiation response to 5.1 MeV Si2+ ions at 300 °C to average 0.1/1/3/100 displacement per atom (dpa) was performed in this study. The height gap between the irradiated area and unirradiated area was measured by atomic force microscopy and used to estimate the volume swelling after irradiation. The swelling of CVD-SiC is basically consistent with the previous reports, which saturates at 1 dpa to a value of 2.1%, while the swelling of the LPS-SiC specimens did not show saturation, even at damage up to 100 dpa, reaching to a value of 5.67%. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy confirmed that the additional volumetric swelling of LPS-SiC over CVD-SiC should come from the sintering additive, i.e., Y3Al5O12 (YAG) in this case. The volumetric swelling of YAG after 100 dpa damage at 300 °C was calculated to be 36.85%, according to the rule of mixtures. The TEM observations and electron diffraction patterns indicated the swelling of YAG was caused by the irradiation-induced amorphization. The influence of YAG on the application of nuclear-grade LPS-SiC are discussed.