Isotope Effects in Uptake of H and D in He Irradiated Oxide Ceramics by Exposure to H2O and D2O Vapors at Room Temperature

Abstract

The uptake of protium and deuterium in He irradiated BaCe0.80Y0.20O3-δ by exposure to H2O and D2O vapors, respectively, and the uptake of protium in D implanted and He irradiated BaCe0.80Y0.20O3-δ and SrCe0.95Yb0.05O3-δ by exposure to atmospheric air at room temperature have been measured in-situ by means of the elastic recoil detection technique (ERD) with 1.7 MeV He+ ions. The uptake speed of protium in BaCe0.80Y0.20O3-δ is found to be by an order of magnitude larger than that in SrCe0.95Yb0.05O3-δ, and those in the D implanted and He irradiated specimens are also found to be much larger than those in as-heated ones. Moreover, the uptake of protium in BaCe0.80Y0.20O3-δ is found to be by a factor of 8.7 larger than that of deuterium, which is a so called isotope effect in the H absorption of the oxide ceramics.The experimental data have been quantitatively analyzed using mass balance equations which involve diffusion, trapping and molecular recombination of free H with trapped one in the bulk according to the one way diffusion model for the DH replacement. The factor of 8.7 in the isotope effect is shown to be composed of the factor of 5.1 in the absorption rate and that of 1.7 in the trapping rate.