Related Experiment Video
Updated: Dec 11, 2025
08:55
Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
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Quantification of High-Temperature Transition Al2 O3 and Their Phase Transformations*
Libor Kovarik1, Mark Bowden2, Amity Andersen2
1Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA, 99352, USA.
Angewandte Chemie (International Ed. in English)
|August 21, 2020
Summary
Quantifying disordered delta-aluminum oxide (δ-Al₂O₃) and twinned theta-aluminum oxide (θ-Al₂O₃) is challenging. A recursive-stacking method accurately models their XRD patterns and phase transformations during high-temperature treatment.
Area of Science:
- Materials Science
- Crystallography
- Solid-State Chemistry
Background:
- High-temperature treatment of gamma-aluminum oxide (γ-Al₂O₃) induces polymorphic transformations.
- Formation of delta-aluminum oxide (δ-Al₂O₃) and theta-aluminum oxide (θ-Al₂O₃) presents microstructural quantification challenges due to structural disorder.
Purpose of the Study:
- To develop and apply an XRD recursive-stacking formalism for quantifying high-temperature transition aluminas.
- To model structural disorder in δ-Al₂O₃ and twinning in θ-Al₂O₃ using this formalism.
Main Methods:
- Formulation of a recursive-stacking methodology for X-ray diffraction (XRD) analysis.
- Application of the formalism to model disorder in δ-Al₂O₃ and twinning in θ-Al₂O₃.
- Study of phase transformation during high-temperature (1050°C) treatment.
Main Results:
- Explicitly accounting for structural disorder is crucial for reliable XRD pattern modeling of transition aluminas.
- The recursive stacking approach successfully models XRD patterns, revealing distinct transformation characteristics for different δ-Al₂O₃ intergrowth modes.
- A significant fraction of δ-Al₂O₃ remains stabilized with θ-Al₂O₃ even after extended high-temperature exposure.
Conclusions:
- The developed XRD recursive-stacking formalism provides a robust method for quantifying microstructural features in high-temperature transition aluminas.
- Understanding the phase transformation dynamics and stabilization mechanisms is key for controlling alumina properties.
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