Abstract：
We use low-dose cryogenic transmission electron microscopy (cryo-TEM) to investigate the atomic-scale structure of antiperovskite Na2NH2BH4 crystals by preserving the room-temperature cubic phase and carefully monitoring the electron dose. Via quantitative analysis of electron beam damage using selected area electron diffraction, we find cryogenic imaging provides 6-fold improvement in beam stability for this solid electrolyte. Cryo-TEM images obtained from flat crystals revealed the presence of a new, long-range-ordered supercell with a cubic phase. The supercell exhibits doubled unit cell dimensions of 9.4 Å × 9.4 Å as compared to the cubic lattice structure revealed by X-ray crystallography of 4.7 Å × 4.7 Å. The comparison between the experimental image and simulated potential map indicates the origin of the supercell is a vacancy ordering of sodium atoms. This work demonstrates the potential of using cryo-TEM imaging to study the atomic-scale structure of air- and electron-beam-sensitive antiperovskite-type solid electrolytes.
摘要：
我们使用低剂量低温透射电子显微镜（cryo-TEM）通过保留室温立方相并仔细监测电子剂量来研究反钙钛矿Na2NH2BH4晶体的原子级结构。通过使用选定区域电子衍射对电子束损伤进行定量分析，我们发现低温成像为这种固体电解质提供了6倍的光束稳定性改善。从平面晶体获得的Cryo-TEM图像揭示了一种新的，具有立方相的远程有序超电池。与X射线晶体学显示的4.7µ×4.7µ的立方晶格结构相比，超级电池的晶胞尺寸为9.4µ×9.4µ。实验图像与模拟电位图之间的比较表明，超电池的起源是钠原子的空位排序。这项工作证明了使用低温TEM成像研究对空气和电子束敏感的反钙钛矿型固体电解质的原子级结构的潜力。
