Thermal transport property in pyrochlore-type and fluorite-type A2B2O7 oxides by molecular dynamics simulation

Pyrochlore-type (P-type) and fluorite-type (F-type) rare-earth A(2)B(2)O(7) -type oxides attract extensive interest in engineering applications in which ultralow thermal conductivity is strongly required for improving energy-utilization efficiency and thermal management. Herein, thermal transport properties of P-type and F-type A(2)B(2)O(7) (A = Y, La, Nd, Sm, Gd, Yb; B = Zr, Ce, Hf) was systematically investigated using molecular dynamics. The thermal conductivity of F-type structures was found to be 0.83 similar to@3.37 W.m(-1)K(-1), which is 30%similar to 50% of that of P-type structures. Such an low thermal conductivity is due to the stronger phonon scattering in F-type structures resulting from the inhomogeneous interatomic bonding. It was also found that the thermal conductivities of F-type A(2)B(2)O(7) being less dependent on temperature and closer to the theoretical minimum values due to the presence of amorphous-like phonon modes. Finally, we identified the optimal compositions in F-type A(2)B(2)O(7) family for achieving lowest thermal conductivity at high temperatures. This study suggests that enhancing the inhomogeneity of interatomic bonding can enable low thermal conductivity in simple-composition materials. (C) 2021 Elsevier Ltd. All rights reserved.