Thermal properties of high-entropy fluorite (Zr0.2Hf0.2Pr0.2La0.2×0.2)O2-δ(X=Dy, Ho, Er, Y, Tm): A first-principles combined with experimental study investigating the influence of size and mass difference effect.

The limited efficiency of traditional trial-and-error experiments has impeded the development and application of high-entropy fluorite oxides in thermal insulation coatings. To solve this problem, a novel entropy descriptor based on first principles is presented to help select candidate components for synthesizing high-entropy fluorite structure oxides. Results show that the compatibilities of 10 single-phase high-entropy fluorite oxides can be accurately predicted based on entropy formation ability. In the studied (Zr, Hf, Pr, La, X) O 2-δ system, a correlation between thermal characteristics and size/mass differences was established by designing the size and mass of X. Specifically, we found that the thermal conductivity is more strongly correlated with the difference in atomic mass, while the coefficient of thermal expansion is strongly correlated with the difference in atomic size. X-ray photoelectron spectroscopy (XPS) analysis shows that the concentration of oxygen vacancy can effectively reduce the thermal conductivity of high-entropy fluorite oxides. In addition, the values of hardness, elastic modulus and thermal conductivity of five single-phase fluorite oxides are successfully predicted by first principles calculation, and the differences between these values and the experimental results are small, which provides a prospective significance for the performance prediction of high-entropy fluorite oxides. Our findings provide a strategy for customizing high-entropy fluorite single-phase oxides with suitable properties to meet the performance requirements of thermal barrier coatings (TBCs). • The DFT calculation provides an entropy descriptor to evaluate the comfiability of high-entropy single-phase fluorite oxides based on their entropy formation capacity. • The hardness, elastic modulus and thermal conductivity of the studied sample are obtained by DFT calculation, and the difference between them and the experimental values is small. • In the (Zr, Hf, Pr, La, X)O 2-δ system, the atomic size difference and atomic mass difference of five single-phase samples were quantified, and their thermal conductivity and thermal expansion values were correlated. [ABSTRACT FROM AUTHOR]