Mechanical response and strain-affected thermal transport in yttria-stabilized zirconia with varying twin-boundary densities and doping concentrations

Yttrium-stabilized zirconia (YSZ) ceramics are widely used in thermal barrier coatings owing to their high-temperature stability and low thermal conductivity. However, the coupled effects of strain, twin boundaries (TBs) densities, and doping concentration on its lattice thermal conductivity (LTC) remain unclear. We used a machine-learning neuroevolution potential with homogeneous nonequilibrium molecular dynamics to examine these factors in YSZ models. Tensile and compressive deformation simulations first confirmed that strains within ± 0.03 remained in the elastic regime for all investigated structures, providing the basis for evaluating strain-dependent LTC. Increasing TB density reduced LTC by up to 58.5%, exceeding the changes observed over the investigated ranges of Y 2 O 3 content and strain. LTC depended more strongly on Y 2 O 3 content in TB-free models than in models containing TBs. Tension and compression produced asymmetric LTC responses, while TB-containing models showed smaller strain-induced changes. Analyses of phonon density of states, participation ratios, and current correlations revealed changes in low-frequency vibrations consistent with greater vibrational localization in TB-containing structures. This study elucidates the synergistic regulation of YSZ thermal transport, providing guidance for the design of low-thermal-conductivity zirconia-based ceramics.