Quenched-in vacancies in single crystalline uranium monocarbide (UC)

Abstract Low-temperature electrical resistivity change due to quenched-in vacancies in single crystalline uranium monocarbide (UC) has been investigated. The formation energies for carbon and uranium vacancies are 1.1 ± 0.3 and 3.7 ± 0.4 eV, respectively. The isochronal annealing curves of quenched-in resistivity, obtained by resistivity measurements at room temperature, show two stages at about 600 and 1100 K, whereas those obtained by resistivity measurements at 77 K exhibit only the stage at 1100 K. The annealing stage at 1100 K is ascribed to the migration of uranium vacancies, of which the activation energy is evaluated as 2.1 ± 0.5 eV. It is found that the quenched-in resistivity depends on temperature; a quadratic temperature dependence is observed below 220 and 160 K for the quenched-in carbon and uranium vacancies, respectively.