Study of thermally induced diffusion mechanisms of implanted helium in the near-surface layers of ceramics based on lithium metazirconate

Abstract

The aim of this study is to determine the thermal exposure effect on the destruction processes of of near-surface layers of ceramics based on lithium metazirconate associated with the diffusion of implanted helium, alongside to determine the effect of the magnesium oxide dopant in low concentrations on restraining diffusion mechanisms during high-temperature irradiation. Interest in this type of ceramics is primarily due to the possibility of expanding the types of lithium-containing ceramics for the production and accumulation of tritium, as well as an increase in stability to degradation processes characteristic of high-temperature operating modes, alongside the accumulation of fission products of nuclear reactions of neutrons with lithium in the form of helium. According to studies carried out using the depth nanoindentation method (measurements along the trajectory of ion movement on a side cleavage), it was found that an elevation in the irradiation temperature leads to a rise in the thickness of the damaged layer, the alteration in which is due to the effects of helium diffusion into depth due to thermal effects. The softening of the near-surface layer during high-temperature irradiation is due to structural changes associated with a growth in deformation distortion of the crystal structure and its swelling, which is most pronounced during high-dose irradiation. At the same time, alterations in the structural features of lithium metazirconate due to the dopant concentration growth during the synthesis of lithium-containing ceramics leads not only to an increase in resistance to softening of the damaged layer, but also to a reduction in the thickness of the diffusion layer in ceramics under high-temperature irradiation.