Preparation and properties of novel (Y, Yb, Zr, Hf, Sn, W)O 2−δ high‐entropy ceramics

A series of (Y, Yb, Zr, Hf, Sn, W)O 2−δ high‐entropy ceramics with varying mole fraction of main elements were synthesized for the first time through the solid‐state reaction synthesis method. The microstructure, phase composition, and properties of the prepared materials were thoroughly analyzed and tested. The results indicate that the phase composition transformed from a single‐phase fluorite structure to a single‐phase C‐type rare earth sesquioxide structure as the mole fraction of +3 cations increases. The thermal conductivity of the prepared high‐entropy ceramics with porosity of 49.8%–50.1% is very low ranging from 0.33 to 0.37 W·m −1 ·K −1 . Among them, the single‐phase C‐type rare earth sesquioxide with a higher oxygen vacancy concentration was employed as a catalyst in the CO 2 hydrogenation reaction, attaining a high CO 2 conversion rate of 82.0%. The obtained results have deepened understanding of the role of oxygen vacancies and have important guiding significance for the study of high‐entropy oxides with fluorite derived structures.