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Updated: Aug 15, 2025

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing
Published on: June 9, 2023
Unusual aliovalent doping effects on oxygen non-stoichiometry in medium-entropy compositionally complex perovskite
Dawei Zhang1, Jiyun Park2, Boyuan Xu3
1Program of Materials Science and Engineering, University of California San Diego, La Jolla, CA, 92093, USA. jluo@alum.mit.edu.
Abstract:
Aliovalent doping of perovskite oxides can tune the oxygen vacancy formation energy. This work discovers normal vs. abnormal aliovalent doping effects on redox behaviors in medium-entropy compositionally complex perovskite oxides (CCPOs) (La1-Sr)(Mn1/3Fe1/3Ti1/3)O3- (LS_MFT) vs. (La1-Sr)(Mn1/3Fe1/3Cr1/3)O3- (LS_MFC). In the LS_MFC series, the oxygen non-stoichiometry range Δδ (= δred - δox) linearly depends on the Sr molar ratio x, while the LS_MFT series shows a V-shape dependence of Δδ on x. This unusual observation is investigated and explained based on the analysis of the energy loss near edge structure (ELNES) in STEM electron energy loss spectroscopy, along with density functional theory (DFT) calculations. In LS_MFC, Cr-L2,3, Mn-L2,3 and Fe-L2,3 peaks have a similar linear shift to higher energy with increasing x, which indicates higher oxidation states of Cr, Mn, and Fe with lower oxygen vacancy formation energies. In LS_MFT, the V-shape of the Δδ vs. x curve is caused by the stable Ti4+ state and a V-shape Mn/Fe valency dependence on x. This study suggests the possible existence of different (including unexpected) coupled aliovalent doping effects in CCPOs with multiple B-site redox active elements.
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