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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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Spinodal Decomposition in the Mg-Al-Fe-O System
Yoshihiro Kusano1, Taiki Furuta1, Ryosuke Maki1
1Department of Applied Chemistry, Okayama University of Science, Ridai-cho 1-1, Kita-ku, Okayama700-0005, Japan.
Inorganic Chemistry
|November 3, 2022
Summary
This study details the preparation and decomposition of a novel magnesium-aluminum-iron spinel solid solution. The material exhibits spinodal decomposition, forming a grid-like microstructure and enhanced magnetization.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Nanotechnology
Background:
- Spinel solid solutions are crucial in various applications due to their tunable properties.
- Understanding the decomposition mechanisms of these materials is key to controlling their microstructure and magnetic behavior.
- Cation-deficient spinels with mixed iron valences present complex phase behaviors.
Purpose of the Study:
- To synthesize a supersaturated Mg-Al-Fe spinel solid solution.
- To investigate its decomposition behavior, microstructure evolution, and magnetic properties.
- To determine the crystallographic relationships upon further thermal treatment.
Main Methods:
- Solid-state reaction at 1573 K followed by quenching.
- Rietveld refinement and thermogravimetry for structural and compositional analysis.
- X-ray diffraction and temperature-dependent magnetization measurements to study spinodal decomposition.
- Transmission electron microscopy for microstructural analysis.
Main Results:
- A cation-deficient spinel (Mg0.50AlFe0.262+Fe1.243+)0.97O4 was successfully prepared.
- Spinodal decomposition below 855 K yielded γ-Fe2O3 and an Fe-poor spinel with enhanced magnetization and a 25 nm grid-like microstructure.
- Heating to 1373 K formed ε-Fe2O3 with specific crystallographic orientation relative to the spinel phase.
Conclusions:
- The Mg-Al-Fe spinel undergoes spinodal decomposition, leading to significant microstructural and magnetic property changes.
- Controlled thermal treatments can induce phase transformations, including the formation of ε-Fe2O3.
- This research provides insights into the phase stability and transformation pathways of complex oxide spinels.
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