Radioluminescence characterization of hot pressed, reaction bonded, and CVD SiC

Radioluminescence for in situ materials characterization: First results on SiC for fusion applications

“…No emission is observed below about 300 nm for the HP and below 500 nm for the RB SiC, consistent with the range of band gap energies for SiC (≈2.2 to 3.3 eV) [18,19]. The high background for the electron irradiation is due to the silica windows [20].…”

“…8). Electron irradiation produces a broad emission at 650 nm, consisting of two bands at 565 and 690 nm [20], while for proton irradiation there is essentially no emission. To explain this marked difference, and also the differences observed in the relative intensities for the HP and RB SiC spectra, one must take into account the 1 MeV proton and 1.8 MeV electron penetration depths (about 10 m and 3000 m respectively), and the optical density (OD) or depth, proportional to the light absorbed in the SiC materials.…”

“…Despite the differences in the irradiation conditions and measuring systems, the two methods give comparable results. Work to try to identify the defects responsible for the observed emissions, effect of dose rate, and cause of the reduction with dose, is now underway [20], as well as work to correlate RL with changes in the electrical conductivity and crystalline structure of the different materials [17]. If successful one may then consider RL as a potential tool for in situ measurement and control of SiC degradation in both fission reactor experiments and future fusion devices.…”

Radiation induced electrical and microstructural degradation at high temperature for HP SiC

“…This change in the behaviour observed for irradiation above 650 • C is also observed in the RL data (Fig. 4) reported elsewhere [4]. These observations indicate that for irradiation up to 650 • C the induced damage in the HP SiC causing a reduction in electrical conductivity and RL is stable, and independent of irradiation temperature.…”

“…However at 800 and 900 • C the degradation rate decreases with increasing irradiation temperature. This equivalent behaviour for the two batches has also been observed during radioluminescence (RL) measurements at 450 • C. The technique, being developed as a way to characterize material degradation during irradiation [4,5], has identified an identical intensity reduction in the HP SiC 600 nm radioluminescence emission for both batches when irradiated at 450 • C, but far less reduction in intensity for irradiation at 800 • C (Fig. 4).…”