Indium hydroxide to oxide decomposition observed in one nanocrystal during in situ transmission electron microscopy studies

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• 作者：Gerhard Miehe ; Stefan Lauterbach ; Hans-Joachim Kleebe ; Aleksander Gurlo ; ^{gurlo@materials.tu-darmstadt.de}
• 关键词：Indium oxide ; In situ ; Transmission electron microscopy ; Kinetics ; Crystallographic transformation ; Decomposition reaction
• 刊名：Journal of Solid State Chemistry
• 出版年：2013
• 出版时间：February, 2013
• 年：2013
• 卷：198
• 期：Complete
• 页码：364-370
• 全文大小：1170 K

文摘

The high-resolution transmission electron microscopy (HR-TEM) is used to study, in situ, spatially resolved decomposition in individual nanocrystals of metal hydroxides and oxyhydroxides. This case study reports on the decomposition of indium hydroxide (c-In(OH)₃) to bixbyite-type indium oxide (c-In₂O₃). The electron beam is focused onto a single cube-shaped In(OH)₃ crystal of {100} morphology with ca. 35 nm edge length and a sequence of HR-TEM images was recorded during electron beam irradiation. The frame-by-frame analysis of video sequences allows for the in situ, time-resolved observation of the shape and orientation of the transformed crystals, which in turn enables the evaluation of the kinetics of c-In₂O₃ crystallization. Supplementary material (video of the transformation) related to this article can be found online at . After irradiation the shape of the parent cube-shaped crystal is preserved, however, its linear dimension (edge) is reduced by the factor 1.20. The corresponding spotted selected area electron diffraction (SAED) pattern representing zone [001] of c-In(OH)₃ is transformed to a diffuse strongly textured ring-like pattern of c-In₂O₃ that indicates the transformed cube is no longer a single crystal but is disintegrated into individual c-In₂O₃ domains with the size of about 5-10 nm. The induction time of approximately 15 s is estimated from the time-resolved Fourier transforms. The volume fraction of the transformed phase (c-In₂O₃), calculated from the shrinkage of the parent c-In(OH)₃ crystal in the recorded HR-TEM images, is used as a measure of the kinetics of c-In₂O₃ crystallization within the framework of Avrami-Erofeev formalism. The Avrami exponent of ¡«3 is characteristic for a reaction mechanism with fast nucleation at the beginning of the reaction and subsequent three-dimensional growth of nuclei with a constant growth rate. The structural transformation path in reconstructive decomposition of c-In(OH)₃ to c-In₂O₃ is discussed in terms of (i) the displacement of hydrogen atoms that lead to breaking the hydrogen bond between OH groups of [In(OH)₆] octahedra and finally to their destabilization and (ii) transformation of the vertices-shared indium-oxygen octahedra in c-In(OH)₃ to vertices- and edge-shared octahedra in c-In₂O₃.