Influence of surface morphology and surface area on release behavior of hydrogen isotopes in LiNbO3

Surface processes have profound influence on tritium release behavior in ceramic breeder materials. In this paper, the release behavior of hydrogen isotopes in LiNbO3 is studied by thermal desorption spectroscopy (TDS) with focusing on the influence of the surface morphology and surface area. It is found that the amount of surface hydroxyl groups is proportional to the specific surface area and can be decreased by smoothing the surface roughness through heating pretreatment at high temperatures. The isotope exchange reaction between the surface hydroxyl groups and water molecules residue in the system is discussed and turns out to proceed fast. The release behavior of hydrogen isotopes in LiNbO3 is compared with that in Li2TiO3 studied in our previous work. It reveals that LiNbO3 and Li2TiO3 have similar surface environment and similar concentration of surface hydroxyl groups with the level of 1020 m−2. The formation mechanism of hydroxyl groups on the surface is discussed and a model to explain the experimental observations is proposed.