Effect of Cr2O3 and NiO dopants in α-Al2O3 on its electrical conductivity under electron irradiation

The electrical conductivity of single crystals of α-Al2O3 doped with Cr2O3 (0.03–2.5 wt%), NiO (0.75 wt%) plus Cr2O3 (0.03–0.15 wt%), and NiO (0.75 wt%) has been measured under 1 MeV electron irradiation at 300 K to investigate the effects of the concentration of impurity and of the depth of impurity levels in forbidden bands on the radiation induced conductivity (RIC). The RIC of Cr2O3 and/or NiO doped α-Al2O3 decreases with increasing concentration of Cr2O3 and/or NiO dopants. The electrical conductivity of 2.5 wt% Cr2O3 doped α-Al2O3 is smaller than any other doped materials tested. The dose rate exponent for Cr2O3 doped α-Al2O3 is smaller than that for NiO plus Cr2O3 doped material, due to deeper trapping centers of Cr (5.8 eV from the conduction band) than those of Ni (2.0 eV). Doping impurities with deep trapping centers are most effective for suppressing RIC.