Thermal stability of oxide–metal nanocomposites is important for designing practical devices for high temperature applications. Here, we study the thermal stability of the self-assembled ordered three-phase Au–BaTiO₃–ZnO nanocomposite by both ex situ annealing under air and vacuum conditions, and by in situ heating in TEM in a vacuum. The study reveals that the variation of the annealing conditions greatly affects the resulting microstructure and the associated dominant diffusion mechanism. Specifically, Au nanoparticles show coarsening upon air annealing, while Au and Zn either form a solid solution, with Zn atomic percentage less than 10%, or undergo a reverse Vapor–Liquid–Solid (VLS) mechanism upon vacuum annealing. The distinct microstructures obtained also show different permittivity response in the visible and near-infrared region, while retaining their hyperbolic dispersion characteristics enabled by their highly anisotropic structures. Such in situ heating study in TEM provides critical information about microstructure evolution, growth mechanisms at the nanoscale, and thermal stability of the multi-phase nanocomposites for future electronic device applications.

中文翻译：

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TEM原位加热自组装有序三相Au–BaTiO3–ZnO纳米复合薄膜的热稳定性

氧化物-金属纳米复合材料的热稳定性对于设计用于高温应用的实用设备非常重要。在这里，我们研究了自组装有序三相的Au-的BaTiO的热稳定性₃由两个-ZnO纳米复合易地空气和真空的条件下退火，以及通过原位在真空中在TEM中加热。研究表明，退火条件的变化极大地影响了所得的微观结构和相关的主要扩散机制。具体而言，金纳米颗粒在空气退火后会变粗，而金和锌要么形成固溶体，锌原子百分比小于10％，要么在真空退火时经历反向的汽-液-固（VLS）机理。获得的独特的微结构在可见光和近红外区域还显示出不同的介电常数响应，同时保留了其高度各向异性的结构所能实现的双曲线分散特性。这样就地 TEM中的加热研究提供了有关微观结构演变，纳米级生长机理以及多相纳米复合材料热稳定性的重要信息，以供将来的电子设备应用。