The ability to resolve spatially and identify chemically atoms in defects would greatly advance our understanding of the correlation between structure and property in materials1. This is particularly important in polycrystalline materials, in which the grain boundaries have profound implications for the properties and applications of the final material2. However, such atomic resolution is still extremely difficult to achieve, partly because grain boundaries are effective sinks for atomic defects and impurities3,4,5, which may drive structural transformation of grain boundaries and consequently modify material properties6,7. Regardless of the origin of these sinks, the interplay between defects and grain boundaries complicates our efforts to pinpoint the exact sites and chemistries of the entities present in the defective regions, thereby limiting our understanding of how specific defects mediate property changes. Here we show that the combination of advanced electron microscopy, spectroscopy and first-principles calculations can provide three-dimensional images of complex, multicomponent grain boundaries with both atomic resolution and chemical sensitivity. The high resolution of these techniques allows us to demonstrate that even for magnesium oxide, which has a simple rock-salt structure, grain boundaries can accommodate complex ordered defect superstructures that induce significant electron trapping in the bandgap of the oxide. These results offer insights into interactions between defects and grain boundaries in ceramics and demonstrate that atomic-scale analysis of complex multicomponent structures in materials is now becoming possible.
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This work was supported in part by a Grant-in-Aid for Scientific Research on Priority Area “Atomic Scale Modification (474)” from MEXT, Japan. We thank T. Mizoguchi for performing electron energy-loss near-edge structure simulations and for discussions, and T. Saito and W. Zeng for experimental assistance. Z.W. acknowledges support by a Grant-in-Aid for Young Scientists (B) (grant no. 22760500) and from IZUMI Science Foundation. M.S. is grateful for a Grant-in-Aid for Scientific Research (C) (grant no. 23560817) and to MURATA Science Foundation for financial support. K.P.M. acknowledges support by a Grant-in-Aid for Young Scientists (B) (grant no. 22740192). S.T. thanks supports from the Nippon Sheet Glass Foundation. Calculations were conducted at ISSP, University of Tokyo.
The authors declare no competing financial interests.
The file contains Supplementary Materials and Methods, Supplementary Text, Supplementary Figures 1-4 with legends, Supplementary Table 1 and additional references. (PDF 922 kb)
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Wang, Z., Saito, M., McKenna, K. et al. Atom-resolved imaging of ordered defect superstructures at individual grain boundaries. Nature 479, 380–383 (2011). https://doi.org/10.1038/nature10593
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