Advances in high entropy oxides: synthesis, structure, properties and beyond

The unique structural features of high entropy oxides (HEOs) offer opportunities for flexible and precise structure control, thereby fostering a broad spectrum of structure-property tuning. This review surveys the extensive research carried out on HEOs, from initial exploration to recent advancement, summarizing progress in the refinement of synthesis techniques, elucidation of the high entropy effect, and understanding of atomic structures at multiple scales. Leveraging the impact of high entropy effect on structures, HEOs exhibit a wide range of properties from thermal to electrical, which have potential applications in fields such as thermoelectrics, dielectrics, energy storage, lithium batteries, catalysis, magnetism and supercapacitors. The correlations between structure and property are analyzed, and potential property-property relations are examined. Finally, we underscore the key challenges and unresolved questions that future research needs to address.