Thermal conductivity of A-site doped pyrochlore oxides studied by molecular-dynamics simulation

Molecular-dynamics simulations are used to compute thermal-conductivity of pyrochlore solid solutions based on Gd2Zr2O7 with substitution on the A-site by La, Y, and Sm ions. Simulation results and theoretical predictions are compared to experimental data where available. We find that simulations predict that the thermal conductivity decreases due to point-defect scattering, but by a much smaller amount than what is observed in experiment. At higher temperatures, we predict that additional point-defect scattering results in very small decreases in the thermal conductivity. While both mass and bond disorder play a role in reducing the thermal conductivity, the simulations suggest that large differences in ionic sizes on the A-site result in biggest effect. We explore the results using a theoretical model based on prior work due to B. Abeles, and find in some cases significant disagreement with our simulated results. The results presented here suggest that additional point-defect disorder will likely be of rather limited value for low thermal-conductivity applications. Finally, we discuss some of the possible explanations for disagreement with experimental observations.