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Updated: Jun 12, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Oscillatory phase transition induced structural extension during iron oxide reduction
Haoyang Fu1,2, Qingze Chen3, Benzhi Min2
1State Key Laboratory for Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Abstract:
Probing the molecular-level redox behavior and mechanism of oxides is essential to developing innovative applications in different fields such as catalysis, but remains a challenge for the scientific community. Using in-situ transmission electron microscopy, here we provide an overall reduction view of single-crystalline α-Fe2O3 with different characteristics from the conventional wisdom of oxide reduction. Specifically, the formation of epitaxial nanoislands with concomitant oscillatory phase transitions (α-Fe2O3→defective γ-Fe2O3→α-Fe2O3) at the subsurface is observed during reduction. The dynamic equilibrium of lattice oxygen at the surface and the limited oxygen replenishment from the deep layer drive the α-Fe2O3→defective γ-Fe2O3 transformation in the subsurface, while the polymorphic transition (defective γ-Fe2O3→α-Fe2O3) spontaneously occurs under heating conditions. Such oscillatory phase transition is accompanied by the release of asymmetric stress, inducing the extension of epitaxial nanoislands. Our work highlights the complexity of reduction by providing an integral picture of oxide reduction, which contributes to the understanding of the site evolution of oxide-based catalysts in their working state.
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