Ion beam analysis of dependence of the D–H replacement speed on trivalent impurity concentration in D‐implanted oxide ceramics exposed to H 2 O vapor at room temperature

The speed of D–H replacement in D‐implanted BaCe 1− X Y X O 3−δ and SrCe 1− X Yb X O 3−δ , exposed to H 2 O vapor at room temperature has been studied as a function of X by use of the ERD technique with 1.7 MeV He + ion beam. The decay curve of D and growth curve of H in the specimens have been measured as a function of exposure time, and the decay constants of D, namely the D–H replacement speeds, have been obtained by fitting the experimental curves to the theoretical curves of D decay and H growth, which are derived from the mass balance equations described on the one‐way diffusion model for the D–H replacement: absorption of H + due to splitting of H 2 O physisorbed at the surface, diffusion of H + and emission of D implanted in the traps as HD molecule due to bulk recombination of H + and subsequent trapping of H + in the vacant trap. It is found for both specimens that the decay constants of D, proportional to the absorption coefficient and the molecular formation coefficient of HD, increase, and after a maximum at X = 0.05–0.1 decrease as X increases, and the absolute experimental values for BaCe 1− X Y X O 3−δ are larger almost by an order of magnitude than those of SrCe 1− X Yb X O 3−δ . These experimental results are discussed in terms of the one‐way diffusion model on D–H replacement and water splitting model at the surface. Copyright © 2006 John Wiley & Sons, Ltd.