The possible negative state of deuterium in LiAlO2 irradiated by 3keV D2+ at higher temperature

Abstract

The existence of hydrogen isotopes in tritium breeding blankets indicates important research value for the realization of tritium self-sufficiency in fusion. The positive states of deuterium trapped by different irradiation defects in LiAlO2 (one of the typical ternary solid tritium breeders) have previously been indicated as O-D vibration absorption peaks in situ FT-IR after deuterium ion irradiation. The present study focused on the possible non-O-D state of deuterium which could not be directly observed by FT-IR in irradiated LiAlO2. In situ FT-IR and thermal desorption spectroscopy (TDS) was performed to single-crystal LiAlO2 irradiated by 3 keV D2+ at 380 K, 440 K and 500 K respectively. The increase of the total intensity of O-D vibration absorption peaks with the release of deuterium as D2 suggests the existence of non O-D state. The non-O-D state is considered to be related to the deuterium trapped by oxygen vacancy. According to the density functional theory calculation, the valence state of hydrogen trapped by the O vacancy in LiAlO2 is -0.865. The transitions of different states (positive versus negative, different positive states) with the irradiation temperature and their effect on the release of chemical forms of deuterium have also been discussed in this paper. All above will contribute to further understanding on existence and behavior of tritium in neutron-irradiated solid breeders.