Trapping and diffusion of hydrogen in iron-doped YO.

YO is a promising material for use as a tritium permeation barrier (TPB) coating and as dispersed particles in oxide dispersion strengthened steels for experimental fusion reactors. By using first-principles approaches, we found that substituting Fe for Y in YO is the most energetically favourable under O-deficient and H-rich conditions, leading to easier formation of the nearby O vacancies. These O vacancies serve as effective trapping sites for H atoms with a formation energy of -2.36 eV. The presence of Fe defects also makes it more difficult for H atoms to migrate in YO from three possible H-related defects. These findings suggest that incorporating Fe into YO could yield a better TPB and provide insight into the improved H trapping ability of YO with Fe dopants.