Su Lei, Chen Xi, Xu Liang, Eldred Tim, Smith Jacob, DellaRova Cierra, Wang Hongjie, Gao Wenpei
State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, 710049, People's Republic of China.
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina27695, United States.
ACS Nano. 2022 Dec 27;16(12):21397-21406. doi: 10.1021/acsnano.2c09760. Epub 2022 Dec 1.
High-entropy oxides (HEOs) have a large tuning space in composition and crystal structures, offering the possibility for improved material properties in applications including catalysis, energy storage, and thermal barrier coatings. Understanding the nucleation and growth mechanisms of HEOs at the atomic scale is critical to the design of their structure and functions but remains challenging. Herein, we visualize the entire formation process of a high-entropy fluorite oxide from a polymeric precursor using atomic resolution gas-phase scanning transmission electron microscopy. The results show a four-stage formation mechanism, including nucleation during the oxidation of a polymeric precursor below 400 °C, diffusive grain growth below 900 °C, liquid-phase-assisted compositional homogenization under a "state of supercooling" at 900 °C, and entropy-driven recrystallization and stabilization at higher temperatures. The atomistic insights are critical for the rational synthesis of HEOs with controlled grain sizes and morphologies and thus the related properties.
高熵氧化物（HEOs）在组成和晶体结构方面具有很大的调控空间，为改善包括催化、能量存储和热障涂层等应用中的材料性能提供了可能性。在原子尺度上理解高熵氧化物的成核和生长机制对于其结构和功能的设计至关重要，但仍然具有挑战性。在此，我们使用原子分辨率气相扫描透射电子显微镜可视化了由聚合物前驱体形成高熵萤石氧化物的整个过程。结果显示了一个四阶段的形成机制，包括在低于400°C的聚合物前驱体氧化过程中的成核、低于900°C的扩散晶粒生长、在900°C的“过冷状态”下液相辅助的成分均匀化，以及在更高温度下熵驱动的再结晶和稳定化。这些原子层面的见解对于合理合成具有可控晶粒尺寸和形貌以及相关性能的高熵氧化物至关重要。
