High-Entropy Oxides: Pioneering the Future of Multifunctional Materials

The high-entropy concept affords an effective method to design and construct customized materials with desired characteristics for specific applications. Extending this concept to metal oxides, high-entropy oxides (HEOs) can be fabricated, and the synergistic elemental interactions result in the four core effects, i.e., the high-entropy effect, sluggish-diffusion effect, severe-lattice-distortion effect, and cocktail effect. All these effects greatly enhance the functionalities of this vast material family, surpassing conventional low- and medium-entropy metal oxides. For instance, the high phase stability, excellent electrochemical performance, and fast ionic conductivity make HEOs one of the hot next-generation candidate materials for electrochemical energy conversion and storage devices. Significantly, the extraordinary mechanical, electrical, optical, thermal, and magnetic properties of HEOs are very attractive for applications beyond catalysts and batteries, such as electronic devices, optic equipment, and thermal barrier coatings. This review will overview the entropy-stabilized composition and structure of HEOs, followed by a comprehensive introduction to the electrical, optical, thermal, and magnetic properties. Then, several typical applications, i.e., transistor, memristor, artificial synapse, transparent glass, photodetector, light absorber and emitter, thermal barrier coating, and cooling pigment, are synoptically presented to show the broad application prospect of HEOs. Lastly, the intelligence-guided design and high-throughput screening of HEOs are briefly introduced to point out future development trends, which will become powerful tools to realize the customized design and synthesis of HEOs with optimal composition, structure, and performance for specific applications.