Irradiation effects and hydrogen behavior in HI and He implanted -LiAlO2 single crystals
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2016 Elsevier B.V. Gamma-phase lithium aluminate (-LiAlO2) is a breeder material for tritium, a necessary substance for strategic stockpile and fusion power systems. A fundamental study of structural evolution and tritium diffusion in -LiAlO2 under displacive irradiation is needed to fully assess the material performance. This study utilizes ion implantation of protium (surrogate for tritium) and helium in -LiAlO2 single crystals at elevated temperatures to emulate the irradiation effects. The results show that at 573K there are two distinct disorder saturation stages to 1dpa without full amorphization; overlapping implantation of H2+ and He+ ions suggests possible formation of gas bubbles. For irradiation to 1021H+/m2 (0.36dpa at peak) at 773K, amorphization occurs at surface with H diffusion and dramatic Li loss; the microstructure contains bubbles and cubic LiAl5O8 precipitates with sizes up to 200nm or larger. In addition, significant H diffusion and release are observed during thermal annealing.