PNNL

Abstract

Gamma-phase lithium aluminate (?-LiAlO2) is a key ceramic used in tritium-producing burnable absorber rods (TPBARs), where efficient thermal transport is critical for heat removal and tritium release. Under irradiation, ?-LiAlO2 partially transforms into LiAl5O8, forming a multiphase microstructure whose impact on thermal transport remains unclear. In this work, molecular dynamics simulations are employed to quantify interfacial thermal resistance in LiAlO2 and LiAl5O8. Bicrystal models are used to evaluate Kapitza resistance at grain boundaries (GBs) across a range of misorientations, revealing an increase in resistance with misorientation angle followed by saturation at higher angles. In addition, heterophase interfaces between LiAlO2 and LiAl5O8 are constructed for multiple orientation relationships to assess interphase thermal resistance. The results show that interphase boundaries exhibit significantly higher Kapitza resistance, on average about twice that of GBs within individual phases. These findings indicate that irradiation-induced phase transformation and the resulting interphase interfaces play a dominant role in limiting thermal transport in these Li ceramics.