Journal of the American Chemical Society
·
2025
·
IF 15.6
Sara Adeeba Ismail,Kazuaki Toyoura,Lulu Jiang,Amir Masoud Dayaghi,Hui Guo,Maxim Avdeev,Huaican Chen,Wen Yin,Wang Hay Kan,Truls Norby,Donglin Han
Ba7Nb4MoO20 is a recently emerging fast oxide ion conductor, attracting increasing attention. It was reported to also show proton conduction in a humid atmosphere, which is, however, opposite to the results in this work. Theoretical calculations indicate that protons can hardly move, being stabilized in the perovskite blocks or trapped in the palmierite layers, which is in line with the experimental evidence of almost no H2O/D2O isotope effect and a negligibly small transport number of protons by EMF measurements up to 800 °C. It is thereby clear that Ba7Nb4MoO20 is almost a pure oxide ion conductor even though it can be hydrated upon exposure to moisture. The hydration in fact stabilizes interstitial oxide ions (O5 site) in the palmierite layers by forming Nb2O9H units, leading to reduced bulk conductivity in the pristine and slightly Nb-rich compositions at <400 °C. However, by heating up over 400 °C, the bulk conductivity in the wet atmosphere surpasses that in the dry one, benefitting from an injection of protons into the perovskite blocks to release free O5 ions for oxide ion conduction, indicating that hydration may provide extra oxide ions to enhance the oxide ion conduction.
研究领域:
材料科学
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固体离子学
·
无机化学
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电化学
·
凝聚态物理
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产品关联
DOI
PubMed
高影响因子
SOLID STATE IONICS
·
2025
·
IF 3.3
Sara Adeeba Ismail,Lulu Jiang,Hui Guo,Wenhao Li,Donglin Han
Ba 7 Nb 4 MoO 20 has acceptably high ionic conductivity at 600–800 °C and is attractive for potential application in high temperature solid state electrochemical devices. Up to now, most of the research focuses on isovalent and donor-doping to improve the electrical properties of Ba 7 Nb 4 MoO 20 . In this work, an acceptor-doping strategy was taken by doping Sc and Zr to partially substitute Nb. More vacant oxygen sites thereby form for charge compensation, leading to the increasing proton concentration following the compositional sequence of hydrated Ba 7 Nb 4 MoO 20 < Ba 7 Nb 3.97 Zr 0.03 MoO 19.985 < Ba 7 Nb 3.97 Sc 0.03 MoO 19.97 . Notably, both the H 2 O/D 2 O isotope effect and EMF measurements indicate that the proton conduction – if there is any – is negligibly small, and the Sc and Zr-doped Ba 7 Nb 4 MoO 20 is essentially an oxide ion conductor in the temperature range studied in this work.
研究领域:
材料科学
·
固体离子学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Materials Chemistry C
·
2024
·Vol. 12
·期 46
·18819-18828
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IF 5.7
Jinyang Li,Wenye Deng,Yan Xue,Ni Ai,Kai Ding,Xianghui Chen,Weiwei Meng,Pengjun Zhao,Aimin Chang,Yongxin Xie
The hexagonal perovskite oxide Ba7Nb4MoO20 is widely studied in chemical devices due to its oxide-ionic conductivity at high temperatures. Ce4+ doping into Ba7Nb4MoO20 was undertaken to optimize small polariton conduction and oxide ionic conductivity simultaneously. Ba7Nb4−xCexMoO20 materials were synthesized via solid phase sintering. XRD patterns indicate a single phase, SEM scans reveal increased densification with higher Ce doping concentrations, and the resistance temperature range expands from 400–900 °C to 300–1100 °C. Hall tests confirm that Ba7Nb4−xCexMoO20 carriers are electrons, indicating n-type conductivity. Nyquist plots illustrate that grain boundary resistance governs complex impedance, which shows gradual oxide ionic conductivity enhancement with rising temperature. The aging drift rate decreases to about 1%, suggesting good stability of Ba7Nb4−xCexMoO20 ceramics. These findings propose a feasible doping strategy for enhancing hexagonal perovskite oxide ceramics.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
Materials Today Chemistry
·
2026
·
IF 6.7
Sara Adeeba Ismail,Wenqi Lei,Lulu Jiang,Donglin Han
Ba 7 Nb 4 MoO 20 is a pure oxide ion conductor in both dry and wet oxygen atmospheres at the operating temperature of solid oxide fuel cells and has the promising potential to be applied as electrolyte materials. In this work, donor-doping trivalent rare earth elements R ( R = Y, Ce, Nd, Ho, Er and Yb) to replace the divalent Ba cations increases oxygen content slightly, but effectively enhances oxide ion conduction. Although the solubility of these dopants is less than x = 0.02 in Ba 7- x M x Nb 4 MoO 20+0.5 x , the Ba 6.98 Er 0.02 Nb 4 MoO 20.01 composition exhibits the highest conductivity, reaching 0.0066 and 0.0085 S cm −1 at 700 and 800 °C, respectively, nearly 6 times higher than that of pristine Ba 7 Nb 4 MoO 20 . H 2 O/D 2 O isotope effect measurement verifies that these materials are essentially pure oxide conductors even in wet atmospheres. It is hard to believe that the trace-level dopant concentration can influence the conduction behavior effectively. However, the slight change in the oxygen content, particularly in the BaO 2 conduction plane, is possible to influence the conductivities. The oxygen occupancy in the O1 and O5 sites thereby seems to be highly sensitive to and dependent on the occupancy of the dopants over the Ba and Nb/Mo sites.
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）