Interplay of irradiation-induced defects with oxygen in 3C-SiC ceramics

Abstract

The oxidation behavior of SiC ceramics is vital to assess its lifetime under extreme conditions within nuclear power systems. Employing systematic first-principles calculations, we studied the oxygen (O) properties in 3C-SiC without and with irradiation-induced defects to understand the oxidation mechanism. Interstitial O (Oint) exhibits two energetically favored states with an energy difference of only 0.02 eV. Two Oint atoms have a strong mutual attraction, with a binding energy reaching 0.80 eV. The stability of O-related defects with charge was investigated. The formation energy of O at the carbon site (OC) is negative, implying that the dissolution of O in the host carbon site is exothermic. The binding strengths of Oint and OC with irradiation-induced defects are notably high. The formation energies of O and carbon vacancy clusters (VCmOn) decrease approximately linearly and turn negative as the number of O increases. The binding energy of VCmOn is still very high, indicating a strong attraction between them. Furthermore, Trapping of O by carbon vacancies may reduce the mobility of O. Electronic properties are analyzed to reveal the interaction mechanism between irradiation-induced defects and O. The irradiation-induced defects may enhance the oxidation of SiC due to the strong binding energies.