Rapid Oxygen Absorption and Transport in Hexagonal Manganites

The hexagonal manganites, h-RMnO₃ where R = Y, Sc, Dy…Lu, are presented as promising materials for mixed ionic and electronic conductivity. With exceptional chemical flexibility on both cation sublattices and robustness with respect to oxygen excess as well as deficiency, hexagonal manganites constitute a most flexible and interesting family of materials for tailoring mixed transport properties. Interestingly, oxygen interstitials migrate through an interstitialcy mechanism with cooperative movements of multiple ions and are more mobile than oxygen vacancies. Density functional theory (DFT) calculations are combined with transport measurements, thermogravimetry and synchrotron X-ray diffraction and X-ray absorption near edge (XANES) to investigate the effect of donor doping to stabilize oxygen interstitials to higher temperatures where the transport kinetics are faster [1], and to construct thermodynamic models [2] for oxygen absorption. Finally, exceptional kinetics of oxygen absorption is reported for high-entropy compositions [3] of hexagonal manganites, even in bulk materials. These properties are insensitive to the exact composition, making such materials highly promising for commercial applications as mixed ionic-electronic conductors.

1. F. H. Danmo et al., «Oxidation Kinetics of Nanocrystalline Hexagonal RMn_1–xTi_xO₃ (R = Ho, Dy)», ACS Appl. Mater. Interfaces. 15 (2023) 42439.
2. F. H. Danmo et al., «Oxygen Absorption in Nanocrystalline h-RMnO₃ (R = Y, Ho, Dy) and the Effect of Ti Donor Doping», Chem. Mater. 35 (2023) 5764.
3. F.H. Danmo et al., «High-Entropy Hexagonal Manganites for Fast Oxygen Absorption and Release» Chem. Mater. 36 (2024) 2711.