Coupled redox and structural evolution of Mo in n LaNb₀.₁Mo₀.₁O₄.₀₅: implications for ionic-electronic transport
Author(s)
Han, Yidong
Huang, Kehan
Berenov, Andrey
Kerherve, Gwilherm
Skinner, Stephen
Type
Journal Article
Abstract
Understanding the redox behavior and structural stability of aliovalent substituents in ionic conductors is critical, as their variable oxidation states can inadvertently introduce electronic conductivity and alter transport mechanisms under different atmospheric conditions. Here, we report the atmosphere-dependent redox behavior and local coordination of Mo in LaNb0.9Mo0.1O4.05, focusing on its influence on phase transition and transport properties, where the as-sintered LaNb0.9Mo0.1O4.05 was systematically annealed under pure O2, pure N2, vacuum (∼1.6 × 10–8 mbar), and 5% H2/N2 at 800 °C for different dwell times. Electron paramagnetic resonance (EPR) spectroscopy results demonstrate the emergence of Mo5+ under 5% H2/N2. In situ X-ray absorption near edge structure (XANES) measurements reveal the reversible redox behavior of Mo, where Mo5+ formed under 5% H2/N2 reoxidizes to Mo6+ upon exposure to static air, while complementary in situ extended X-ray absorption fine structure (EXAFS) analysis shows that the Nb coordination environment also transitions from prototypical LaNbO4 structure under reducing conditions back to the Mo-substituted LaNbO4 structure upon reoxidation. This change of the oxidation states of Mo could correspondingly alter the band structure of the sample, which further enhances charge transport: the sample annealed in 5% H2/N2 for 24 h exhibits a reduced activation energy and increased electronic conductivity. These results highlight a strong coupling among substituent redox flexibility, local structure, and transport properties, providing an understanding of tailoring the properties of ionic conductors through controlled redox environments.
Date Issued
2025-12-23
Date Acceptance
2025-12-03
Citation
Chemistry of Materials, 2025, 37 (24), pp.9975-9786
ISSN
0897-4756
Publisher
American Chemical Society
Start Page
9975
End Page
9786
Journal / Book Title
Chemistry of Materials
Volume
37
Issue
24
Copyright Statement
© 2025 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0 .
License URL
Publication Status
Published
Date Publish Online
2025-12-09