Ion Conduction In Solids Research Articles

Revised Centrality Measures Tell a Robust Story of Ion Conduction in Solids.

The three most commonly used centrality measures in network theory have been adapted to consider ion conduction time rather than the number of steps. Flow-IN centrality highlights sites with the largest flow of ions from the nearest neighbor sites. Return-flow centrality highlights sites with a fast rate of first returns for the conducting ion. Flow-through centrality highlights which sites support significant flow of conducting ions and appears more robust to removal of the most central vertices. Exploring these centrality measures with the sample system of proton conduction in yttrium doped barium zirconate shows flow-through centrality to provide a robust picture with high contrast between sites involved in the most probable long-range periodic conduction paths and kinetic Monte Carlo trajectories versus sites rarely visited. The flow-through centrality, including all paths further highlights that when the most central proton site is filled, the remaining highest flow-through centrality sites are nearby, corroborating earlier studies suggesting proton pair motion. Finally, while both return-flow and flow-through centrality measure images deteriorate with noise, image restoration is possible when a detailed balance is used to calculate the smaller rate constant in a forward/backward pair.

Effect of Dispersion of Platinum Nanoparticles in Strontium Zirconate and Strontium Cerate Proton Conductors

The interface of two materials having different work function leads to the development of space charge, resulting in the change of defect equivalence and hence the change in the charge carrier concentration. Another possibility lies in the formation of strain at the interface resulting in the change of the mobility of ionic charge carriers. If we can use these effects for the enhancement of ionic conductivity, introduction of hetero-interface is a potential guideline for designing new ion conduction in solids. We have reported previously that when Pt nanoparticles precipitate in proton conducting SrZr0.9Y0.1O3-δ (SZY), the electrical conductivity decreases markedly due to nanoionics effects; small amount of Pt can be dissolved into the Zr site and becomes zero-valent upon exposure to hydrogen [1]. Such a change in the macroscopic electrochemical properties is considered as a result of the unique microscopic electrochemical properties of the nanoscale space charge layer generated in the vicinity of the interface when the Pt nanoparticles are precipitated [2]. Using electrochemical spectroscopy, SrCe0.95Yb0.05O3-δ (SCYb) and Sr(Zr,Ce,Y)O3 proton conducting oxide thus doped with Pt were investigated with the aim to clarify the effects and mechanism of the Pt/oxide interface on the electrical properties of proton conducting oxide. Pt-doped proton conducting oxides were prepared by combustion synthesis method. The electrical conductivity of Pt-SZY and Pt-SCYb measured at 800 °C under 1% H2 and air atmospheres revealed a reversible nanoionics phenomenon as a result of precipitation and dissolution of platinum nanoparticles (Fig.1). The electrical conductivity then decreases significantly when the atmosphere is change to hydrogen for Pt-SZY. In the case of Pt-SCYb an increase in the conductivity can be seen for the same changes of the atmosphere. This change in electrical conductivity has been explained by the effect of precipitated Pt particles. In other words, a proton deficient region is formed in the vicinity of the interface between Pt and SZY whereas at the interface between Pt and SCYb, there is no such influence. Also, this result can be applied to deepen understanding of the reaction at the electrodes of the electrochemical cell. Comparing the electrode overvoltage when SZY and SCYb are used for the electrolyte in a cell using Pt as the electrode, SZY is several orders of magnitude larger than SCYb [3]. The reason for this can be explained if it is thought that the region where protons are not present is formed near the interface of Pt / SZY like as the case of Pt nanoparticles disperse in the bulk of SZY. On the other hand, the reason why the overvoltage at Pt/SCYb interface is smaller than that at SZY is considered to be a reasonable result of the loss of protons not taking place significantly near the interface.

The First Combined Experimental and Theoretical Evaluation of Tetravalent Cation Conduction in a Solid

AbstractTetravalent tellurium ion conduction in solids has been demonstrated in α‐Te2MoO7 by both experimental and theoretical means for the first time. Although it has been commonly considered that the Te4+ ion will not conduct appreciably in solids due to its high valency, such conduction can be successfully achieved in solid α‐Te2MoO7, which has a 2D layered structure conducive to ion migration. The measured Te4+ ion conductivity in solid α‐Te2MoO7 (1.0 × 10–2 S cm–1 at 530 °C) reaches the threshold required for practical applications. Evidence for Te4+ ion conduction in α‐Te2MoO7 is provided both directly by DC electrolysis results and theoretically by MEM analysis.

Oxide nitrides: From oxides to solids with mobile nitrogen ions

The possibility of fast nitrogen ion conduction in solids is reviewed. Promising electrolytes based on three different base compounds are in the focus of this contribution: Zirconium oxide nitrides, tantalum oxide nitrides and mayenite-based materials. All aspects ranging from preparation methods, crystal structures (ideal and defect structure, also at elevated temperatures), transport properties (ionic and electronic conductivity, transference numbers, diffusion) and correlations between structure and physical properties are presented and discussed, in part also in relation to theoretical calculations. Fluorite-type quaternary oxide nitrides of zirconium are proven to be the first known materials with high nitrogen ion mobility. They can be described as fast mixed oxygen/nitrogen conductors but are limited due to the low maximum nitrogen/oxygen ratio achievable. Corresponding phases based on stabilized tantalum oxide nitrides have a superior N/O ratio but show poor thermal stability. For the development of a pure nitrogen ion conductor a different approach has also been investigated: Some cage compounds, in particular mayenite, allow the substitution of oxygen anions not tightly bound in the framework by nitrogen ions. Some of the obtained N-containing phases exhibit an outstanding electrical conductivity at low temperatures. Possible devices and applications such as a new type of a nitrogen sensor and an ammonia-producing fuel cell are introduced and discussed.

ChemInform Abstract: A Discovery of Tetravalent Ge4+ Ion Conduction in Solids.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Discovery of Tetravalent Ge4+ Ion Conduction in Solids

Abstract Tetravalent Ge4+ ion conduction in solids was first demonstrated by selecting a NASICON-type GeNb(PO4)3 solid and partially replacing P5+ ion in GeNb(PO4)3 with Si4+ ion to expand the crystal lattice, which allows for realization of a Ge4+ ion with high valence and electronegativity. Among the Ge1+x⁄4NbP3−xSixO12 solids prepared, it was found that Ge41⁄40NbP2.9Si0.1O12 (x=0.1) solid showed the highest Ge4+ ion conductivity.

First Discovery of Tetravalent Ti4+ Ion Conduction in a Solid

Pure tetravalent Ti4+ ion conduction in solids was first demonstrated for the Ti(Nb1−xWx)5/(5+x)(PO4)3 (x ≤ 0.2) solid with a three-dimensional NASICON-type structure. Strict selection of the crystal structure and constituent elements enabled high Ti4+ ion conductivity for the Ti(Nb0.8W0.2)5.0/5.2(PO4)3 solid.

High-Trivalent Rare Earth Ion Conduction in Solids Based on NASICON-Type Phosphate

Abstract Trivalent rare earth ion conductors of the (R0.05Zr0.95)80⁄79Nb(PO4)3 (R: rare earths) series with NASICON-type structures were successfully prepared and the optimum size of ion-conducting pathways for rare earth ions in (R0.05Zr0.95)80⁄79Nb(PO4)3 solids was investigated. The most suitable ion-conducting pathway for rare earth ion conduction in this series was realized for R=Dy and the highest conductivity of 3.2×10−4 S cm−1 at 600 °C was obtained for (Dy0.05Zr0.95)80⁄79Nb(PO4)3 solids. Since R3+ ion conduction was strongly dependent on the ratio of conducting R3+ ion size to crystal lattice size (VR3+⁄Vlattice; we denote this ratio as A ratio in this article), it was clear that the A ratio is a key factor to optimize R3+ ion conduction in NASICON-type structures.

Nano-Ionics: Trivial and Non-Trivial Size Effects on Ion Conduction in Solids

Abstract The significance of nano-size effects for ion transport in solids is highlighted both experimentally – by presenting various results of recent investigations – and theoretically – by considering expected size effects using a top-down approach. It is helpful to distinguish between trivial size effects (effects that equally occur at single interfaces but are augmented by the high interfacial density) and true size effects (involving local modifications due to the finite boundary conditions). The latter ones essentially include space charge overlap and structural interference leading to two characteristic sizes with respect to defect chemistry. The contribution also briefly touches upon effects of dimensionality and shape as well as of discreteness of carrier distribution.

Extraordinary High Trivalent Al3+ Ion Conduction in Solids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

電池材料 リチウムスピネルＺｎ１‐ｘＬｉｘＦｅ２‐ｘＴｉｘＯ４（ｘ＝０．０〜１．０）のイオン分布

The substitution of Li+ for Zn2+ and Ti4+ for Fe3+ in ZnFe2O4 with the spinel stype structure was adopted to obtain the fundamental understanding of the Li ion conduction in solids. The cation distribution of the compound was investigated at the starting research. The XRD patterns indicated the formation of the solid solution, Zn1-xLixFe2-xTixO4 and the lattice parameter decreased linearly with the increase of x in accordance with the ionic radius for each cation. Above x = 0.6 a slight curvature appeared in the composition dependence of the lattice parameter. The Rietveld analysis determined the cation distribution for the present system. It can be written as Zn1-xFex[8a][Lix/2Fe1-xTix/2][16d]2O4 (for x 0.5). The observed change in the composition dependence of the lattice parameter is caused by the change of the cation distribution in the spinel structure. In addition, the iron distribution for the present system was confirmed by the Mossbauer spectroscopy. The electrochemical lithium insertion was also discussed.

Trivalent ion conducting solid electrolytes

A trivalent ion conduction in solids was realized with Sc 2(WO 4) 3-type structure by the consideration of the stability and size of mobile trivalent ions and a structure to reduce the electrostatic interaction between the framework and the mobile ionic species as much as possible. Among the tungstates and the molybdates with the Sc 2(WO 4) 3-type structure, Sc 2(WO 4) 3 and Sc 2(MoO 4) 3 were found to hold the most suitable lattice size for trivalent ion migration in the individual series. By the dc electrolysis and EPMA measurements, the mobile species was clearly identified to be trivalent ions in the Sc 2(WO 4) 3-type structure.

Microstructural aspects of oxygen ion conduction in solids

The microstructure of solid electrolyte ceramics plays a key role in defining the level of ionic conduction of the material. The polycrystalline nature and the metastable state of most practically useful materials require that the conducting ion must negotiate a series of interfacial features during the conducting process. These features may either enhance or impede the conducting ions and include such things as precipitates, microdomains, various zone configurations and the ubiquitous grain boundaries. By combining the technique of impedance spectroscopy with extensive microstructural analysis, it has been shown that it is possible to develop a comprehensive picture of how some of these features influence the conductivity and to use this knowledge to improve the materials design. A number of examples to illustrate this approach will be discussed, including some recent results on the effect of Al 2O 3 additions to zirconia ceramics — work that began in Professor Steele’s group almost 20 years ago.

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc2(WO4)3-Type Structure

To realize a trivalent ion conduction in solids, the Sc2(WO4)3-type structure was chosen on the basis of the mobile trivalent ions and the structure which reduces the electrostatic interaction between the framework and the mobile trivalent ionic species as much as possible. The typical conductivity of the rare earth tungstates R2(WO4)3 (R = Sc, Y, and Er−Lu) with the Sc2(WO4)3-type structure was found to be on the order of 10-5 S cm-1 at 600 °C. Among the rare earth tungstates, Sc2(WO4)3 (σ600°C = 6.5 × 10-5 S cm-1, Ea = 44.1 kJ mol-1) was found to be the most suitable size for the ionic conduction with regard to the relation between the mobile ion radius and the lattice size. The rare earth ion conducting characteristics were investigated by means of the rare earth concentration cell measurements and dc electrolyses. The electromotive force measurements with the Sc−Y binary alloy and the yttrium tungsten bronze as the electrodes strongly suggest the possibility of the trivalent ion conduction of rare ear...

Trivalent Ion Conduction in the Scandium Tungstate-Type Structure

ABSTRACTThe realization of a trivalent ion conduction in solids was successful by selecting the Sc2(WO4)3-type structure from the consideration of the mobile trivalent cations and the structure which decreases the electrostatic interaction between the migrating trivalent ionic species and the framework structure as much as possible. Among the rare earth tungstates, Sc2(WO4)3 (σ600°C=6.5× 10−5 S'cm−1, Ea=44.1 kJ.mo−1) was found to hold the most suitable size for the trivalent ion migration in the relation between the mobile ion size and the lattice volume. The ion conducting characteristics of rare earths were studied by means of both the polarization and dc electrolysis techniques. The mobile species was demonstrated to be the trivalent ions in the Sc2(WO4)3-type structure. By the dc electrolysis, the mobile ion species was definitely identified to be the trivalent ions in the Sc2(WO4)3-type tungstates. In addition, the demonstration of a macroscopic Al3+ ion conduction in the tungstate structure was directly accomplished.

ChemInform Abstract: Direct Evidence for Trivalent Ion Conduction in Solids.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Direct Evidence for Trivalent Ion Conduction in Solids

Abstract In order to realize a higher valency ion conduction in solids, the Sc2(WO4)3 material which possesses a larger tunnel size for ion migration was selected to reduce the electrostatic interaction and the single crystals of Sc2(WO4)3 were grown to eliminate grain boundary effects found in polycrystalline state. By both the alternative and direct current measurements, a direct evidence of Sc3+ trivalent ion migration in single crystal Sc2(WO4)3 has been successfully demonstrated.

Fast ion conductors: future trends

The characteristics of various fast ion conductors (FICs) are reviewed with an emphasis on correlating their structural and transport properties. This approach leads toward an improved understanding of the cause of fast ion conduction in solids and suggests avenues for future research and applications. All three categories of fast ion conductors—extrinsic, intrinsic and amorphous—are briefly reviewed. Special attention is focused on (a) some of the newer, intrinsically disordered oxygen conductors such as α-Ta 2O 5 and the pyrochlore system Gd 2(Zr xTi 1−x) 2O 7, (b) amorphous cation conductors both organic and inorganic and (c) two-phase composite systems. Some of the more promising new FICs are discussed in relation to applications which will probably become increasingly important before the end of the century including fuel cells, batteries, sensors, electrochemical pumps and smart windows.

East ion conduction: some theoretical issues

Recent progress in the theoretical understanding of fast ion conduction in solids is discussed, with emphasis placed on mechanistic behavior and on the characteristic features of particular sorts of solid electrolytes. We consider soft framework materials such as α-AgI, and hard framework materials such as β″-alumina. In each case, we discuss which theoretical methods have been used to investigate mechanisms of conductivity and diffusion, and some of the physical insights which have been gleaned on the mechanism of ionic conductivity. Comments are also made on glassy conductors such as glassy lithium aluminosilicate, and polymeric ionic conductors such as polyethylene oxide/lithium triflate. Since different characteristic timescales, and characteristic energies, are appropriate for these different classes of materials, varying theoretical methods have been used, and should be used, to understand the ionic motion. Particular concepts, such as dynamic percolation in polymer electrolytes, strong memory effects in soft framework materials, strongly correlated liquid-like diffusion in hard framework materials and disorder-induced weadening of correlations in glassy materials are pointed out. We speculate briefly on the role of very strong interionic correlations in causing possible domain-wall conduction, a process that goes well beyond any hopping description. We briefly discuss some special behavior observed in certain classes of solid electrolytes, such as fractal behavior, “universal dielectric response”, the mixed alkali effect in glasses, and the “Liang effect”, which is the enhancement of ionic conductivity by inclusion of an insulating second phase. Remarks are ventured both on theoretical methodology and on the usefulness of models for understanding, predicting and designing solid electrolyte behavior.