  High entropy carbides ceramics with randomly-distributed multiple principal
cations have shown high temperature stability, low thermal conductivity, and
possible radiation tolerance. While chemical disorder has been shown to
suppress thermal conductivity in these materials, little investigation has been
made on the effects of additional, extrinsically-generated structural defects
on thermal transport. Here, (Zr$_{0.25}$Ta$_{0.25}$Nb$_{0.25}$Ti$_{0.25}$)C is
exposed to Zr ions to generate a micron-scale, structural-defect-bearing layer.
The reduction in lattice thermal transport is measured using laser
thermoreflectance. Conductivity changes from different implantation
temperatures suggest dislocation loops contribute little to phonon scattering
while nanoscale defects serve as effective scatterers, offering a pathway for
thermal engineering.

Materials Science