Preparation and properties of novel (Y, Yb, Zr, Hf, Sn, W)O2−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.