Abstract: High-entropy ceramic oxides (HEOs) have emerged as promising candidates for next-generation thermal barrier coatings (TBCs) due to their exceptional thermal stability and intrinsically low thermal conductivity, originating from pronounced structural and chemical disorder. In contrast to conventional ceramics, phonon-disorder scattering dominates thermal transport in HEOs, which is not well captured in traditional theoretical and computational models. This study proposes a new quantitative predictive model for thermal conductivity based on the supercell phonon-unfolding (SPU) method. Using rocksalt-structured HEOs as the representative material system, the lattice disorder has been comprehensively investigated using first-principles calculations. The disorder is well reflected in the phonon spectra obtained through the SPU method. Using the phonon linewidth as the quantitative indicator of the phonon-disorder scattering rate, a predictive model for the thermal conductivity of HEOs has been established. The model is shown to quantitatively predict thermal conductivity values of the rocksalt HEOs, in excellent agreement with experimental measurements and atomistic simulation results. This work establishes a new computational pathway for the quantitative evaluation of thermal conductivity for high-entropy ceramic oxides, as well as other complex material systems where phonon-disorder scattering dominates thermal transport, thus providing a powerful tool enabling high-throughput screening and accelerated design of novel materials for next-generation TBCs.

Key words: High-entropy ceramics, Thermal barrier coating, Thermal conductivity, Supercell phonon-unfolding, First-principles calculations