Isotope Effects in Diffusions of H and D in Hydrogen Isotope Exchange in Oxide Ceramics

Autor:	Bun Tsuchiya, Hiroyasu Iwahara, Emi Iizuka, Kazuo Soda, Kenji Morita
Rok vydání:	2002
Předmět:	Nuclear and High Energy Physics Ion beam Hydrogen Diffusion Radiochemistry Analytical chemistry chemistry.chemical_element Elastic recoil detection Nuclear Energy and Engineering chemistry Deuterium Kinetic isotope effect Physics::Atomic Physics Irradiation Molecular beam
Zdroj:	Journal of Nuclear Science and Technology. 39:359-362
ISSN:	1881-1248 0022-3131
DOI:	10.1080/18811248.2002.9715203
Popis:	In order to clarify the contribution of the hydrogen ion diffusion to the hydrogen isotope exchange at room temperature in a proton-conducting ceramics SrCe 0.95 Yb 0.05 O 3-δ , the concentration change of hydrogen isotopes, H and D, in the ceramics has been measured by elastic recoil detection analysis as a function of the irradiation time of a 0.5-keV molecular hydrogen ion beam after the hydrogen isotope implantation. The rate for the decrease of D implanted with 5-keV D + 2 beam on the 0.5-keV H + 2 irradiation is 1.1-1.4 times larger than that or H implanted with 5-keV H + 2 beam on the 0.5-keV D + 2 irradiation. With use of mass balance equations (rate equations) and the observed rates for the isotope decrease, the ratio of the diffusion constants for H and D is estimated as 2-4, which is larger than the classical ratio of 2 but comparable with a reported ratio, 2.5, of ionic conductivities for H and D at room temperature. The present results suggest that the observed large isotope effect in the hydrogen exchange in the ceramics may arise mainly from difference in the dissociative adsorption rate for water molecules at the surface rather than the rate for the hydrogen ion diffusion.
Databáze:	OpenAIRE
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