Flux creep after thermal neutron irradiation of uranium-doped oriented compacts of YBa2Cu3Ox

Fission fragment damage was introduced by thermal neutron irradiation into aligned, sintered powder samples of YBa₂Cu₃O_x with uranium additions of 0.08 wt % UO₂. This resulted in an increase in the intragranular critical current and a decrease in flux creep. Flux creep of the magnetization M exhibited simple log time dependence and was characterized by absolute and normalized slopes as functions of magnetic field and temperature. Before irradiation, the slopes were strongly field dependent and showed peaks as a function of temperature. After irradiation the slopes were much less field dependent and the peaks were suppressed. Both the magnitude and the field dependence of the creep were improved. Apparent pinning potentials at 0.8 T increased by a factor of about 2 on irradiation, for temperatures from 10 to 35 K. These increases in the apparent pinning potentials are attributed to the damage caused by the travel of the fission fragments through the crystal.