Electrical conduction in irradiated pyrolytic graphite

Fast neutron irradiation at about 20°C to a dose of 10 18 neutrons per cm 2 reduces the a -axis conductivity of recrystallized pyrolytic graphite by a factor of about 3.1, but increases the c -axis conductivity by a factor of about 5.2. Using the conductivity in these two directions as an indicator, the annealing behaviour has been studied by a combination of isochronal and isothermal techniques up to 1350°C. The annealing kinetics found are similar to data reported for reactor grade graphite, but data on the resistivity-temperature characteristics for various degrees of residual damage are found to be useful in discussing the electrical properties of disordered pyrolytic graphites. In particular it appears that interestitial atoms assist conduction in the c -axis, but reduce a -axis conductivity up to 800°K, whereas vacancies exert a dominant effect only below 400°K.