Influence of irradiation-induced point defects on the dissolution and diffusion properties of hydrogen in α-Al2O3: a first-principles study

As a result, higher H retention can be expected, which is consistent with the experimental results. Moreover, by calculating several different diffusion pathways of H-defect complexes and the corresponding diffusion coefficient, it can be inferred that H atoms and vacancy-type point defects can hardly diffuse as a bound entity. Therefore, isolated vacancy-type irradiation-induced point defects can trap multiple H atoms to form H-defect complexes and impede the diffusion process of H, which can enhance the efficiency of protection against H permeation through α-Al2O3 TPB.

However, the minimum diffusion barrier for OiH− migration to the first nearest neighbor O interstitial site is 0.44 eV, which is so low that OiH− can migrate quickly at room temperature. This fast diffusion pathway for H could be the underlying mechanism for the low efficiency in preventing H permeation through irradiated α-Al2O3. Our results provide a sound theoretical explanation for recent experimental results of H permeation in α-Al2O3 under irradiation environment.