Radiation induced modification of electrical conductivity for three types of SiC

Recent results for 1.8 MeV electron irradiated hot pressed SiC at 450 deg. C showed significant reduction in the volume electrical conductivity and a marked loss of crystalline structure by 420 MGy, with relatively low displacement damage (6 x 10-5 dpa). Hot pressed SiC now irradiated at 290, 450, and 650 deg. C, shows the same reduction in volume electrical conductivity with no temperature dependence. Conductivity reduction is larger for irradiation without an electric field. In contrast results for reaction bonded and CVD SiC irradiated at 450 deg. C show initial rapid increases in electrical conductivity below 100 MGy (20% for RB, ∼100% for CVD), followed in the case of CVD SiC by a more gradual increase up to 420 MGy. These observations highlight the potentially important role of ionization, and suggest that some material modifications observed for low dose neutron irradiation in experimental reactors may be due to the ionizing radiation.