Measurement of radiation-enhanced diffusion of la in single crystal thin film CeO₂

The diffusion of La, a trivalent cation dopant, actinide surrogate, and high-yield fission product, in CeO₂, a UO₂ nuclear fuel surrogate, during 1.8 MeV Kr⁺ ion bombardment over a temperature range from 673 K to 1206 K has been measured with secondary ion mass spectroscopy. The diffusivity under these irradiation conditions has been analyzed with a model based on a combination of sink-limited and recombination-limited kinetics. This analysis yielded a cation vacancy migration energy of Emv ∼ 0.4 eV below ∼800 K, were recombination-limited kinetics dominated the behavior. The thermal diffusivity of La in the same system was measured over a range of 873-1073 K and was characterized by an activation enthalpy of Ea=Efv+Emv∼1.4eV. The measurement of both the migration enthalpy and total activation enthalpy separately allows the vacancy formation enthalpy on the cation sublattice to be determined; Efv ∼ 1 eV. The mixing parameter under energetic heavy-ion bombardment at room temperature was measured as well and found to be ∼4 × 10^-5 nm ⁵/eV.