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Updated: Sep 11, 2025
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Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides
Published on: May 29, 2018
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Selective Oxidation and Cr Segregation in High-Entropy Oxide Thin Films
Le Wang1, Krishna Prasad Koirala1, Shuhang Wu2
1Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
Nano Letters
|August 11, 2025
Summary
Strontium doping in high-entropy oxides (HEOs) alters chromium oxidation states and causes segregation. Precise control over growth conditions is crucial for tuning HEOs for electrocatalyst applications.
Area of Science:
- Materials Science
- Solid State Chemistry
- Nanotechnology
Background:
- High-entropy oxides (HEOs) exhibit remarkable compositional flexibility and structural stability.
- HEOs are promising candidates for advanced energy and catalytic applications.
Purpose of the Study:
- Investigate the impact of strontium (Sr) doping on B-site cation oxidation states, local composition, and structure.
- Analyze Sr doping effects in epitaxial La1-xSrx(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 thin films.
Main Methods:
- X-ray spectroscopies (e.g., XPS, XAS) to determine cation oxidation states.
- Atomic-resolution scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX) for compositional and structural analysis.
Main Results:
- Sr doping promotes the oxidation of chromium (Cr) from Cr3+ to Cr6+ and partially oxidizes cobalt (Co) and nickel (Ni).
- Manganese (Mn) and iron (Fe) oxidation states remained unchanged (Mn4+, Fe3+).
- Significant Cr segregation was observed, with surface enrichment and interface depletion, alongside partial amorphization in heavily doped samples.
Conclusions:
- Oxidation-induced migration of smaller, high-valence Cr cations drives segregation during film growth.
- Charge compensation, local strain, and compositional fluctuations are critical factors in HEOs.
- Tailoring growth conditions is essential for controlling surface composition and electronic structure in HEOs for improved electrocatalyst design.
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