Effect of Grain Size on Hydrogen Isotope Behavior in LiNbO₃

Understanding the tritium behavior in breeder materials is essential for the safe and economic operation of fusion reactor. In this paper, the effect of grain size on bulk diffusion of hydrogen isotope in ternary lithium oxide was studied. LiNbO₃ single-crystal samples of different grain sizes were used: cubic samples (a) 4.7×4.7×4.7 mm³, (b) 1.5×1.5×1.5 mm³, and (c) 0.46×0.46×0.46 mm³; powder sample (d) 45 m (a.v). With the grain size of cubic samples decreasing, it was clearly observed that the position of TDS peak related to bulk diffusion moved to a lower temperature because of shorter diffusion path. In comparison with computational simulation based on a diffusion model, a fair agreement between experiment and calculation was obtained.