Su Lei, Huyan Huaixun, Sarkar Abhishek, Gao Wenpei, Yan Xingxu, Addiego Christopher, Kruk Robert, Hahn Horst, Pan Xiaoqing
Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA.
KIT-TUD-Joint Research Laboratory Nanomaterials, Technical University Darmstadt, 64287, Darmstadt, Germany.
Nat Commun. 2022 Apr 29;13(1):2358. doi: 10.1038/s41467-022-30018-y.
The enhanced compositional flexibility to incorporate multiple-principal cations in high entropy oxides (HEOs) offers the opportunity to expand boundaries for accessible compositions and unconventional properties in oxides. Attractive functionalities have been reported in some bulk HEOs, which are attributed to the long-range compositional homogeneity, lattice distortion, and local chemical bonding characteristics in materials. However, the intricate details of local composition fluctuation, metal-oxygen bond distortion and covalency are difficult to visualize experimentally, especially on the atomic scale. Here, we study the atomic structure-chemical bonding-property correlations in a series of perovskite-HEOs utilizing the recently developed four-dimensional scanning transmission electron microscopy techniques which enables to determine the structure, chemical bonding, electric field, and charge density on the atomic scale. The existence of compositional fluctuations along with significant composition-dependent distortion of metal-oxygen bonds is observed. Consequently, distinct variations of metal-oxygen bonding covalency are shown by the real-space charge-density distribution maps with sub-ångström resolution. The observed atomic features not only provide a realistic picture of the local physico-chemistry of chemically complex HEOs but can also be directly correlated to their distinctive magneto-electronic properties.
在高熵氧化物（HEOs）中纳入多主阳离子时增强的成分灵活性，为拓展氧化物中可及成分和非常规性质的边界提供了机会。在一些块状HEOs中已报道了具有吸引力的功能特性，这归因于材料中的长程成分均匀性、晶格畸变和局部化学键合特征。然而，局部成分波动、金属 - 氧键畸变和共价性的复杂细节很难通过实验可视化，尤其是在原子尺度上。在此，我们利用最近开发的四维扫描透射电子显微镜技术研究了一系列钙钛矿型HEOs中的原子结构 - 化学键合 - 性质相关性，该技术能够在原子尺度上确定结构、化学键合、电场和电荷密度。观察到成分波动的存在以及金属 - 氧键随成分的显著畸变。因此，具有亚埃分辨率的实空间电荷密度分布图显示了金属 - 氧键合共价性的明显变化。观察到的原子特征不仅为化学复杂的HEOs的局部物理化学提供了真实写照，而且还可以直接与其独特的磁电性质相关联。
