Selective Oxidation and Cr Segregation in High-Entropy Oxide Thin Films

Wang, Le; Koirala, Krishna Prasad; Wu, Shuhang; Shi, Jueli; Kao, Hsin-Mei; Ho, Andrew; Choi, Min-Ju; Mantilla, Alexander B. C.; Qi, Dongchen; Tadich, Anton; Bowden, Mark E.; Matthews, Bethany E.; Zhou, Hua; Yang, Yang; Chang, Chih-hung; Zhu, Zihua; Wang, Chongmin; Du, Yingge

doi:10.1021/acs.nanolett.5c03196

Title: Selective Oxidation and Cr Segregation in High-Entropy Oxide Thin Films

Journal Article · Mon Aug 11 00:00:00 UTC 2025 · Nano Letters

DOI: https://doi.org/10.1021/acs.nanolett.5c03196 · OSTI ID:2587806

^[1]; Koirala, Krishna Prasad ^[1]; Wu, Shuhang ^[2]; Shi, Jueli ^[1];

^[3]; Ho, Andrew ^[4]; Choi, Min-Ju ^[1]; Mantilla, Alexander B. C. ^[1];

^[2];

^[5];

^[1];

^[6];

^[7];

^[8];

^[1];

^[1]

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Queensland University of Technology, Brisbane, QLD (Australia)
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Oregon State University, Corvallis, OR (United States)
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Santa Rosa Junior College, CA (United States)
Australian Nuclear Science and Technology Organisation (ANSTO), Melbourne, VIC (Australia). Australian Synchrotron
Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
Oregon State University, Corvallis, OR (United States)

High-entropy oxides (HEOs) offer exceptional compositional flexibility and structural stability, making them promising materials for energy and catalytic applications. Here, in this study, we investigate Sr doping effects on B-site cation oxidation states, local composition, and structure in epitaxial La_1–xSr_x(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃ thin films. X-ray spectroscopies reveal that Sr doping preferentially promotes Cr oxidation from Cr³⁺ to Cr⁶⁺, partially oxidizes Co and Ni, while leaving Mn⁴⁺ and Fe³⁺ unchanged. Atomic-resolution scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy shows pronounced Cr segregation, with depletion at the interface and enrichment at the surface, along with partial amorphization in heavily Sr-doped samples. This segregation is likely driven by oxidation-induced migration of smaller, high-valence Cr cations during growth. These findings highlight the critical interplay between charge compensation, local strain, and compositional fluctuations in HEOs, indicating that precise control over growth conditions is critical for tuning their surface composition and electronic structure toward more robust electrocatalyst design.

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Research Organization:: Brookhaven National Laboratory (BNL), Upton, NY (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), Biological and Environmental Research (BER)

Grant/Contract Number:: AC05-76RL01830; SC0012704

OSTI ID:: 2587806

Report Number(s):: BNL--228879-2025-JAAM

Journal Information:: Nano Letters, Journal Name: Nano Letters Journal Issue: 33 Vol. 25; ISSN 1530-6992; ISSN 1530-6984

Publisher:: American Chemical Society (ACS)Copyright Statement

Country of Publication:: United States

Language:: English

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Title: Selective Oxidation and Cr Segregation in High-Entropy Oxide Thin Films

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