Spurgeon Steven R, Sassi Michel, Ophus Colin, Stubbs Joanne E, Ilton Eugene S, Buck Edgar C
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99352;
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352.
Proc Natl Acad Sci U S A. 2019 Aug 27;116(35):17181-17186. doi: 10.1073/pnas.1905056116. Epub 2019 Aug 9.
Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in [Formula: see text] surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during [Formula: see text] surface oxidation.
氧缺陷决定了一系列材料的性能，这些材料涵盖催化、量子计算和核能等领域。对于核燃料循环中锕系氧化物的安全使用、储存和处置而言，理解和控制这些缺陷尤为重要，因为它们的氧化态会影响燃料寿命、稳定性以及地下水污染情况。然而，这些系统中尚未被充分理解的纳米级波动可能导致与整体氧化行为产生显著偏差。在此，我们描述了如何使用像差校正扫描透射电子显微镜和电子能量损失谱来解析[化学式：见原文]表面局部氧缺陷环境的变化。我们观察到较大的图像对比度和光谱变化，这些变化反映了纳米尺度间隙氧含量存在相当大的梯度，我们通过第一性原理计算和图像模拟对其进行了量化。这些发现揭示了在复杂的近表面空间分布中前所未有的过量氧水平，为[化学式：见原文]表面氧化过程中的缺陷形成途径和动力学提供了更多见解。
