Abstract Since the 1970s, high-resolution transmission electron microscopy (HRTEM) is well established as the most appropriate method to explore the structural complexity of niobium tungsten oxides. Today, scanning transmission electron microscopy (STEM) represents an important alternative for performing the structural characterization of such oxides. STEM images recorded with a high-angle annular dark field (HAADF) detector provide not only information about the cation positions but also about the distribution of niobium and tungsten as the intensity is directly correlated to the local scattering potential. The applicability of this method is demonstrated here for the characterization of the real structure of Nb7W10O47.5. This sample contains well-ordered domains of Nb8W9O47 and Nb4W7O31 besides little ordered areas according to HRTEM results. Structural models for Nb4W7O31 and twinning occurring in this phase have been derived from the interpretation of HAADF-STEM images. A remarkable grain boundary between well-ordered domains of Nb4W7O31 and Nb8W9O47 has been found that contains one-dimensionally periodic features. Furthermore, short-range order observed in less ordered areas could be attributed to an intimate intergrowth of small sections of different tetragonal tungsten bronze (TTB) based structures.

中文翻译：

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四方钨青铜型铌钨氧化物的共生

摘要 自 1970 年代以来，高分辨率透射电子显微镜 (HRTEM) 已成为探索铌钨氧化物结构复杂性的最合适方法。今天，扫描透射电子显微镜 (STEM) 代表了执行此类氧化物结构表征的重要替代方法。用高角度环形暗场 (HAADF) 探测器记录的 STEM 图像不仅提供有关阳离子位置的信息，还提供有关铌和钨分布的信息，因为强度与局部散射电位直接相关。这里证明了该方法的适用性，用于表征 Nb7W10O47.5 的真实结构。根据 HRTEM 结果，除了很少的有序区域之外，该样品还包含 Nb8W9O47 和 Nb4W7O31 的有序域。Nb4W7O31 的结构模型和发生在这一阶段的孪晶是从 HAADF-STEM 图像的解释中推导出来的。已发现 Nb4W7O31 和 Nb8W9O47 的有序域之间的显着晶界包含一维周期性特征。此外，在较不有序的区域中观察到的短程有序可归因于不同四方钨青铜 (TTB) 基结构的小部分的紧密共生。