Impact of Dislocation Loops on Thermal Conductivity of Fluorite Oxides

Impact of dislocation lines on thermal conductivity of semiconductor and insulators has received attention due to their relevance to thermal management of electronic devices. We discuss influence of dislocation loops characterized by circular extra plane of atoms introduced by exposing cerium and thorium dioxide to energetic protons. Experimental observations suggest that (111) faulted loops in the fluorite oxides have a dramatic impact on thermal conductivity. While these results are consistent with classical acoustic limit formulation of phonon interaction with defects, they reveal unusual behavior, where the impact of individual interstitials making up the faulted loop on thermal conductivity is weaker than when they are clustered into a faulted loop. The nonequilibrium molecular dynamics simulations considering different orientations predict noticeably weaker reduction in conductivity due to loops. We attribute these observations to a long-range strain field of the loops not adequately captured by finite size of the simulation cell.