Modulated Structure Determination and Ion Transport Mechanism of Oxide-Ion Conductor CeNbO4+δ

CeNbO4+δ, a family of oxygen hyperstoichiometry materials with varying oxygen contents (CeNbO4, CeNbO4.08, CeNbO4.25, CeNbO4.33) and showing mixed electronic and oxide ionic conduction, have been known for four decades. However, the oxide ionic transport mechanism has remained unclear due to the unknown atomic superstructures of CeNbO4.08 and CeNbO4.33. Here, we determinate the complex superstructures of CeNbO4.08 (89 unique atoms), <a>CeNbO4.25 (75 unique atoms) and CeNbO4.33 (19 unique atoms) by using recently developed continuous rotation electron diffraction (cRED) technique from nano single crystals. </a><a>The Ce cationic size contraction upon oxidation in CeNbO4+δ allows not only excess oxygen incorporation into the CeNbO4 host lattice at the interstitial site within the Ce cation chains (referred to as Oi), but also relaxation of the NbOn polyhedra in CeNbO4.08, CeNbO4.25, CeNbO4.33 being bridged through mixed corner/edge-sharing in 3-dimentional directions. </a>Two kinds of oxide ion migration events are identified in CeNbO4.08 and CeNbO4.25 phases by molecular dynamic simulations, which form long-rang 3-dimensional migration pathway through the interstitial sites Oi via a synergic-cooperation knock-on mechanism involving continuous breaking and reformation of Nb2O9 units. However, the excess oxygen in the CeNbO4.33 phase hardly migrates because of ordered distribution of high-concentration excess oxide ions. The relationship between the structure and oxide ion migration for the whole series of CeNbO4+d compounds elucidated here provides a direction for the performance optimization of these compounds and the development of oxygen hyperstoichiometric materials for wide variety of applications.

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Modulated structure determination and ion transport mechanism of oxide-ion conductor CeNbO4+δ

Nature Communications ◽

10.1038/s41467-020-18481-x ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Jian Li ◽

Fengjuan Pan ◽

Shipeng Geng ◽

Cong Lin ◽

Lukas Palatinus ◽

...

Keyword(s):

Performance Optimization ◽

Transport Mechanism ◽

Ionic Conduction ◽

Excess Oxygen ◽

High Concentration ◽

Ion Migration ◽

Modulated Structure ◽

Ion Conductor ◽

Oxide Ion Conductor ◽

Oxide Ion

Abstract CeNbO4+δ, a family of oxygen hyperstoichiometry materials with varying oxygen content (CeNbO4, CeNbO4.08, CeNbO4.25, CeNbO4.33) that shows mixed electronic and oxide ionic conduction, has been known for four decades. However, the oxide ionic transport mechanism has remained unclear due to the unknown atomic structures of CeNbO4.08 and CeNbO4.33. Here, we report the complex (3 + 1)D incommensurately modulated structure of CeNbO4.08, and the supercell structure of CeNbO4.33 from single nanocrystals by using a three-dimensional electron diffraction technique. Two oxide ion migration events are identified in CeNbO4.08 and CeNbO4.25 by molecular dynamics simulations, which was a synergic-cooperation knock-on mechanism involving continuous breaking and reformation of Nb2O9 units. However, the excess oxygen in CeNbO4.33 hardly migrates because of the high concentration and the ordered distribution of the excess oxide ions. The relationship between the structure and oxide ion migration for the whole series of CeNbO4+δ compounds elucidated here provides a direction for the performance optimization of these compounds.

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Multinuclear Solid-State NMR Studies of Ionic Conduction Mechanisms in Low-Cost and Rare-Earth-Free Superior Fast Oxide-Ion Conductor Sr3-3xNa3xSi3O9-1.5x

ECS Meeting Abstracts ◽

10.1149/ma2015-01/1/196 ◽

2015 ◽

Keyword(s):

Rare Earth ◽

Solid State ◽

Solid State Nmr ◽

Ionic Conduction ◽

Low Cost ◽

Nmr Studies ◽

Ion Conductor ◽

Oxide Ion Conductor ◽

Conduction Mechanisms ◽

Oxide Ion

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Transition Metal D$ LaGaO3 Perovskite Fast Oxide Ion Conductor and Intermediate Temperature Solid Oxide Fuel Cell

MRS Proceedings ◽

10.1557/proc-575-283 ◽

1999 ◽

Vol 575 ◽

Cited By ~ 2

Author(s):

Tatsumi Ishihara ◽

Takaaki Shibayama ◽

Miho Honda ◽

Hiroyasu Nishiguchi ◽

Yusaku Takita

Keyword(s):

Transition Metal ◽

Power Density ◽

Ionic Conduction ◽

Ion Conductivity ◽

Large Power ◽

Ion Conductor ◽

Oxide Ion Conductor ◽

Oxide Ion Conductivity ◽

Wide Range ◽

Oxide Ion

ABSTRACTDoping transition metal cation is known to enhance the electric conduction of solid electrolytes, however, the ionic conduction can be improved by doping the small amount of transition metal, in particular, doping Co is effective for improving the oxide ion conductivity. In this investigation, oxide ion conductivity of LaGaO3 based oxide doped with Co were investigated in detail. It was found that LaGaO3 doped with Co for Ga site (LSGMC) show a notable oxide ion conductivity over a wide range of oxygen partial pressures, although a hole conduction was appeared by addition of excess amount of Co. Considering the electrical conductivity and transport number of oxide ion, the optimized composition of LSGMC seems to be existed at La0.8.Sr0.2, Ga0.8,.Mg0.115 CO0.085O3. Power generation characteristics of fuel cells was greatly improved by using LSGMC for electrolyte and extremely large power density can be obtained on both H2- O2 and H2-air cells. In particular, the maximum power density was attained to a value of 1.53 and 0.50 W/cm2 at 1073 and 873 K, respectively, on H2–O2 cell when the thickness of electrolyte was 0.18 mm. Furthermore, almost similar large power density was attained when air was used as oxidant. The high power density of cell demonstrated in this study suggests that the operating temperature of SOFC can be decreased by using LSGMC for electrolyte.

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