Fe effect on hydrogen interactions with intrinsic point defects and hydrogen migration in α-Al2O3 based tritium permeation barriers

α-Al ₂O ₃ based coatings are the first candidate for tritium permeation barriers (TPBs) in fusion reactors, and the impurity effect on hydrogen resistance is one of the major concerns. In the present work, Fe effect on hydrogen interactions with intrinsic point defects and hydrogen migration in α-Al ₂O ₃ under the TPB service condition has been investigated based on first-principles calculations. It is found that Fe is unfavorable for the formation of vacancy-type defects and defect complex [V _Al-H] in α-Al ₂O ₃, yet beneficial for the formation of H-related defects H _i and H _O. The H trapping ability by vacancy type defects in α-Al ₂O ₃ is lowered after Fe doping. H _i is the main diffusion species in Fe-doped α-Al ₂O ₃, and Fe is favorable for the H migration in α-Al ₂O ₃, which will be unfavorable for H resistance of α-Al ₂O ₃ based TPBs. During the H _i migration in Fe-doped α-Al ₂O ₃, one step of screw motion is involved, in which the forming and breaking of the H-Fe and H-O bonds occur.