Hydrogen Isotope Dissolution and Release Behavior of Rare Earth Oxides
M. Khalid Hossain, Kenichi Hashizume, Shinnosuke Jo, Kaname Kawaguchi, Yuji Hatano
Abstract
Hydrogen release behavior from rare earth oxides (REOs) (Y2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Er2O3, and Yb2O3) exposed to 133 Pa of deuterium (D2) gas or 2 kPa of heavy water (D2O) vapor at 873 K for 5 h was examined using thermal desorption spectroscopy. Hydrogen solubility and diffusivity in Y2O3, Gd2O3, Dy2O3, Er2O3, and Yb2O3 exposed to a deuterium-tritium gas mixture (5% to 7% T, 133 Pa) at 873 K and 973 K for 5 h were determined using a tritium imaging plate method. The structural and morphological properties of sintered disk specimens of those REOs were evaluated using an X-ray diffractometer and a scanning electron microscope. From the obtained results, the REO materials were clearly categorized into two kinds in terms of their crystal structure and hydrogen solubility: Monoclinic specimens of Sm2O3, Eu2O3, and Gd2O3 had relatively high hydrogen solubility and diffusivity, while cubic Y2O3, Dy2O3, Er2O3, and Yb2O3 had lower ones. The present study suggests that the cubic REOs could be suitable in a nuclear fusion reactor as the tritium barrier materials.