Temperature dependence of the D-H replacement rates in D-implanted oxide ceramics exposed to H₂O vapor

Temperature dependence of the D-H replacement rates in D-implanted BaCe_0.9Y_0.1O_3-δ exposed to H₂O vapor has been studied by means of the ERD technique with MeV He⁺ ion beam. It is found that the decay constant of D, namely D-H replacement rate increases monotonically as the specimen temperature is elevated from the implantation (room) temperature up to 50 °C. The concentration of H absorbed in the specimen by the D-H replacement is also found to be almost comparable to the implantation concentration of D, while the concentration of D implanted and H absorbed by the D-H replacement are reduced when the specimen is annealed in the vacuum. The apparent activation energy for the decay constant of D at elevated temperatures is found to be 0.70 eV, which is considerably higher than the one which is expected to be obtained at cooling temperatures below the implantation temperature. No reduction in the concentration of H absorbed by the D-H replacement is ascribed to enough fast absorption of H due to splitting of H₂O at the surface, in comparison with thermal release of D and H. The higher activation energy for the decay constant of D is also ascribed to the contribution of thermal detrapping to emission of D₂ and HD due to the local molecular recombination of D and H detrapped thermally with D and H in traps.