Thermal Stability of High‐Entropy Oxide Thin Films: From Stability Mechanisms to Materials Design

ABSTRACT High‐entropy oxide (HEO) thin films, as an important branch of high‐entropy material systems, have shown broad application prospects in energy, catalysis, protective coatings, and other fields, owing to their unique compositional design strategy and potentially excellent multifunctionality. Thermal stability is a core factor determining their high‐temperature service performance and reliability, and has become a key research focus and challenge in this field. This paper reviews recent progress in the thermal stability of HEO thin films, focusing on material‐system classification, major influencing factors, and underlying mechanisms. It highlights key processes, including phase evolution, elemental segregation, grain growth, and interfacial reactions, and examines how the four core effects regulate thermal stability. The review also outlines potential applications of HEO thin films in high‐temperature and multifunctional environments. Current studies show that HEO thin films generally offer superior structural stability compared with conventional oxide films; however, long‐term thermal cycling reliability and accurate performance prediction under extreme conditions remain important challenges. Future research should integrate high‐throughput experimentation and machine learning to optimize compositional space, and further explore material composition optimization, defect engineering, and stability under coupled multi‐field conditions, thereby promoting the practical application of HEO thin films in high‐temperature functional devices.