scholarly journals Modulated order in ionic conductors: a fine line between helping and hindering

2014 ◽  
Vol 70 (a1) ◽  
pp. C228-C228
Author(s):  
Chris Ling
Keyword(s):  
Ionic Conduction ◽  
Proton Conductor ◽  
Neutron Diffraction Pattern ◽  
Ionic Conductors ◽  
Ion Conductor ◽  
Oxide Ion Conductor ◽  
3 Dimensional ◽  
Modulated Structures ◽  
Superspace Formalism ◽  
The Relationship

"Solid-state ionic conduction relies on essentially conflicting structural properties: long-range crystalline order, to provide structural stability (as fuel cell membranes, battery cathodes etc.); and short-range disorder, to provide smooth conduction pathways without deep local energy minima that could trap the conducting species. Materials that combine these features are generally metastable, and prone to ordering into complex modulated structured that can only be described in (3+n) dimensions using the superspace formalism. Such ordering would normally be expected to seriously compromise conduction properties. However, low-temperature modulated structures can be effective and stable precursors to high-temperature ionic conductors - and, in some cases, can coexist with regions of local disorder that actually enhance conduction. The relationship between modulated order and ionic conduction is relatively little studied, but some of our recent work points to its potential importance. This presentation will focus on two examples: the (3+3)-dimensional commensurately modulated proton conductor Ba4Nb2O9.1/3H2O; [1,2] and the (3+3)-dimensional incommensurately modulated oxide ion conductor ""Type II"" Bi2O3.xNb2O5 (for which a single-crystal neutron diffraction pattern and the refined structure are shown below). [3] The aim is to show how modulated structures can be designed and manipulated to optimise technological performance by striking a balance between stabilising the overall framework while destabilising the conduction pathways."

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

2019 ◽  
Author(s):  
Jian Li ◽  
Fengjuan Pan ◽  
Shipeng Geng ◽  
Cong Lin ◽  
Mathieu Allix ◽  
...  
Keyword(s):  
Performance Optimization ◽  
Transport Mechanism ◽  
Ionic Conduction ◽  
Excess Oxygen ◽  
High Concentration ◽  
Ion Migration ◽  
Ion Conductor ◽  
Oxide Ion Conductor ◽  
Continuous Rotation ◽  
Oxide Ion

<p>CeNbO<sub>4+δ</sub>, a family of oxygen hyperstoichiometry materials with varying oxygen contents (CeNbO<sub>4</sub>, CeNbO<sub>4.08</sub>, CeNbO<sub>4.25</sub>, CeNbO<sub>4.33</sub>) 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 CeNbO<sub>4.08</sub> and CeNbO<sub>4.33</sub>. Here, we determinate the complex superstructures of CeNbO<sub>4.08 </sub>(89 unique atoms), <a>CeNbO<sub>4.25 </sub>(75 unique atoms) and CeNbO<sub>4.33</sub> (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 CeNbO<sub>4+δ</sub> allows not only excess oxygen incorporation into the CeNbO<sub>4</sub> host lattice at the interstitial site within the Ce cation chains (referred to as O<sub>i</sub>), but also relaxation of the<sub> </sub>NbO<sub>n</sub> polyhedra in CeNbO<sub>4.08</sub>, CeNbO<sub>4.25</sub>, CeNbO<sub>4.33</sub> being bridged through mixed corner/edge-sharing in 3-dimentional directions. </a>Two kinds of oxide ion migration events are identified in CeNbO<sub>4.08</sub> and CeNbO<sub>4.25</sub> phases by molecular dynamic simulations, which form long-rang 3-dimensional migration pathway through the interstitial sites O<sub>i</sub> via a synergic-cooperation knock-on mechanism involving continuous breaking and reformation of Nb<sub>2</sub>O<sub>9</sub> units. However, the excess oxygen in the CeNbO<sub>4.33</sub> 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 CeNbO<sub>4+</sub><sub>d</sub> 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.</p>

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

1999 ◽  
Vol 575 ◽  
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.

scholarly journals Dual Oxygen Defects in Layered La1.2Sr0.8−xBaxInO4+δ (x = 0.2, 0.3) Oxide-Ion Conductors: A Neutron Diffraction Study

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1624 ◽  
Author(s):  
Loreto Troncoso ◽  
Carlos Mariño ◽  
Mauricio D. Arce ◽  
José Antonio Alonso
Keyword(s):  
Oxygen Vacancies ◽  
Parent Compound ◽  
Layered Perovskite ◽  
Total Conductivity ◽  
Interstitial Oxygen ◽  
Ionic Conductors ◽  
Ion Conductor ◽  
Oxide Ion Conductor ◽  
Oxide Ion ◽  
Oxygen Atoms

The title compounds exhibit a K2NiF4-type layered perovskite structure; they are based on the La1.2Sr0.8InO4+δ oxide, which was found to exhibit excellent features as fast oxide-ion conductor via an interstitial oxygen mechanism. These new Ba-containing materials were designed to present a more open framework to enhance oxygen conduction. The citrate-nitrate soft-chemistry technique was used to synthesize such structural perovskite-type materials, followed by annealing in air at moderate temperatures (1150 °C). The subtleties of their crystal structures were investigated from neutron powder diffraction (NPD) data. They crystallize in the orthorhombic Pbca space group. Interstitial O3 oxygen atoms were identified by difference Fourier maps in the NaCl layer of the K2NiF4 structure. At variance with the parent compound, conspicuous oxygen vacancies were found at the O2-type oxygen atoms for x = 0.2, corresponding to the axial positions of the InO6 octahedra. The short O2–O3 distances and the absence of steric impediments suggest a dual oxygen-interstitial mechanism for oxide-ion conduction in these materials. Conductivity measurements show that the activation energy values are comparable to those typical of ionic conductors working by simple vacancy mechanisms (~1 eV). The increment of the total conductivity for x = 0.2 can be due to the mixed mechanism driving both oxygen vacancies and interstitials, which is original for these potential electrolytes for solid-oxide fuel cells.

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

2019 ◽  
Author(s):  
Jian Li ◽  
Fengjuan Pan ◽  
Shipeng Geng ◽  
Cong Lin ◽  
Mathieu Allix ◽  
...  
Keyword(s):  
Performance Optimization ◽  
Transport Mechanism ◽  
Ionic Conduction ◽  
Excess Oxygen ◽  
High Concentration ◽  
Ion Migration ◽  
Ion Conductor ◽  
Oxide Ion Conductor ◽  
Continuous Rotation ◽  
Oxide Ion

<p>CeNbO<sub>4+δ</sub>, a family of oxygen hyperstoichiometry materials with varying oxygen contents (CeNbO<sub>4</sub>, CeNbO<sub>4.08</sub>, CeNbO<sub>4.25</sub>, CeNbO<sub>4.33</sub>) 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 CeNbO<sub>4.08</sub> and CeNbO<sub>4.33</sub>. Here, we determinate the complex superstructures of CeNbO<sub>4.08 </sub>(89 unique atoms), <a>CeNbO<sub>4.25 </sub>(75 unique atoms) and CeNbO<sub>4.33</sub> (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 CeNbO<sub>4+δ</sub> allows not only excess oxygen incorporation into the CeNbO<sub>4</sub> host lattice at the interstitial site within the Ce cation chains (referred to as O<sub>i</sub>), but also relaxation of the<sub> </sub>NbO<sub>n</sub> polyhedra in CeNbO<sub>4.08</sub>, CeNbO<sub>4.25</sub>, CeNbO<sub>4.33</sub> being bridged through mixed corner/edge-sharing in 3-dimentional directions. </a>Two kinds of oxide ion migration events are identified in CeNbO<sub>4.08</sub> and CeNbO<sub>4.25</sub> phases by molecular dynamic simulations, which form long-rang 3-dimensional migration pathway through the interstitial sites O<sub>i</sub> via a synergic-cooperation knock-on mechanism involving continuous breaking and reformation of Nb<sub>2</sub>O<sub>9</sub> units. However, the excess oxygen in the CeNbO<sub>4.33</sub> 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 CeNbO<sub>4+</sub><sub>d</sub> 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.</p>

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

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.

A transmission electron microscopic study of structural transitions in fast ionic conductors

1987 ◽  
Vol 45 ◽  
pp. 156-157
Author(s):  
R. B. Queenan ◽  
P. K. Davies
Keyword(s):  
Optical Properties ◽  
Ionic Conduction ◽  
Recent Observation ◽  
Ionic Conductivities ◽  
Sodium Aluminate ◽  
Two Dimensions ◽  
Ionic Conductors ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Trivalent Cations

Na ß“-alumina (Na1.67Mg67Al10.33O17) is a non-stoichiometric sodium aluminate which exhibits fast ionic conduction of the Na+ ions in two dimensions. The Na+ ions can be exchanged with a variety of mono-, di-, and trivalent cations. The resulting exchanged materials also show high ionic conductivities.Considerable interest in the Na+-Nd3+-ß“-aluminas has been generated as a result of the recent observation of lasing in the pulsed and cw modes. A recent TEM investigation on a 100% exchanged Nd ß“-alumina sample found evidence for the intergrowth of two different structure types. Microdiffraction revealed an ordered phase coexisting with an apparently disordered phase, in which the cations are completely randomized in two dimensions. If an order-disorder transition is present then the cooling rates would be expected to affect the microstructures of these materials which may in turn affect the optical properties. The purpose of this work was to investigate the affect of thermal treatments upon the micro-structural and optical properties of these materials.

Further Evidence for Energy Landscape Flattening in the Superionic Argyrodites Li6+xP1−xMxS5I (M = Si, Ge, Sn)

2019 ◽  
Author(s):  
Saneyuki Ohno ◽  
Bianca Helm ◽  
Till Fuchs ◽  
Georg Dewald ◽  
Marvin Kraft ◽  
...  
Keyword(s):  
Solid State ◽  
Activation Barrier ◽  
Energy Landscape ◽  
General Mechanism ◽  
Ionic Conductors ◽  
Energy Storage Devices ◽  
Ion Conductor ◽  
Storage Devices ◽  
Open Questions ◽  
Sudden Decrease

<p>All-solid-state batteries are promising candidates for next-generation energy storage devices. Although the list of candidate materials for solid electrolytes has grown in the past decade, there are still many open questions concerning the mechanisms behind ionic migration in materials. In particular, the lithium thiophosphate family of materials has shown very promising properties for solid-state battery applications. Recently, the Ge-substituted Li<sub>6</sub>PS<sub>5</sub>I argyrodite was shown to be a very fast Li-ion conductor, despite the poor ionic conductivity of the unsubstituted Li<sub>6</sub>PS<sub>5</sub>I. Therein, the conductivity was enhanced by over three orders of magnitude due to the emergence of I<sup>−</sup>/S<sup>2−</sup>exchange, <i>i.e.</i>site-disorder, which led to a sudden decrease of the activation barrier with a concurrent flattening of the energy landscapes. Inspired by this work, two series of elemental substitutions in Li<sub>6+<i>x</i></sub>P<sub>1−<i>x</i></sub><i>M<sub>x</sub></i>S<sub>5</sub>I (<i>M</i>= Si and Sn) were investigated in this study and compared to the Ge-analogue. A sharp reduction in the activation energy was observed at the same <i>M</i><sup>4+</sup>/P<sup>5+</sup>composition as previously found in the Ge-analogue, suggesting a more general mechanism at play. Furthermore, structural analyses with X-ray and neutron diffraction indicate that similar changes in the Li-sublattice occur despite a significant variation in the size of the substituents, suggesting that in the argyrodites, the lithium substructure is most likely influenced by the occurring Li<sup>+</sup>– Li<sup>+</sup>interactions. This work provides further evidence that the energy landscape of ionic conductors can be tailored by inducing local disorder.</p>

scholarly journals Sodium, Silver and Lithium-Ion Conducting β″-Alumina + YSZ Composites, Ionic Conductivity and Stability

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 293
Author(s):  
Liangzhu Zhu ◽  
Anil V. Virkar
Keyword(s):  
Ion Exchange ◽  
Electrochemical Impedance ◽  
Ionic Conductivities ◽  
Lithium Ion ◽  
Co2 Corrosion ◽  
Ionic Conductors ◽  
Ion Conductor ◽  
Sensor Applications ◽  
Potential Applications ◽  
Ion Conducting

Na-β″-alumina (Na2O.~6Al2O3) is known to be an excellent sodium ion conductor in battery and sensor applications. In this study we report fabrication of Na- β″-alumina + YSZ dual phase composite to mitigate moisture and CO2 corrosion that otherwise can lead to degradation in pure Na-β″-alumina conductor. Subsequently, we heat-treated the samples in molten AgNO3 and LiNO3 to respectively form Ag-β″-alumina + YSZ and Li-β″-alumina + YSZ to investigate their potential applications in silver- and lithium-ion solid state batteries. Ion exchange fronts were captured via SEM and EDS techniques. Their ionic conductivities were measured using electrochemical impedance spectroscopy. Both ion exchange rates and ionic conductivities of these composite ionic conductors were firstly reported here and measured as a function of ion exchange time and temperature.

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