Showing papers on "Ionic conductivity published in 1995"
966 citations
TL;DR: In this article, a comparison between the properties of composite polymeric electrolytes containing inorganic and organic fillers is made based on conductivity data obtained from impedance spectroscopy and structural characteristics based on FT-IR, NMR, DSC and EDX.
346 citations
TL;DR: In this paper, the activation energy and conductivity for lanthanoid silicates of the Ln10(SiO4)6O3 solid solution series and related compounds were investigated.
Abstract: Ionic conductivities have been investigated for lanthanoid silicates of the Ln10(SiO4)6O3 solid solution series and related compounds. The activation energy and conductivity at 500 °C were estimated to be 69 kJ mol–1 and 1.8 × 10–4 S cm–1 for La10(SiO4)6O3 and 71 kJ mol–1 and 1.5 × 10–4 S cm–1 for Nd10(SiO4)6O3. The a and c lattice constants of the hexagonal phase decreased with decreasing radius of the Ln3+ ion for Ln10(SiO4)6O3(Ln = La, Nd, Sm, Gd and Dy). The activation energy increased and the conductivity decreased when Ln3+ ions with smaller ionic radii were used. The sole carrier in these materials is the O2– ion.
334 citations
TL;DR: In this paper, the evolution of transport properties with temperature is discussed in relation to structure, revealing a series of phase transitions between ambient temperature and 1000 °C, which is confirmed by measurement of water vapour transfer in a cell in which the perovskite is exposed to wet hydrogen on both sides.
331 citations
TL;DR: The ionic conductivities of cerium oxide doped with oxides of the entire rare earth series (except Pm) were measured using ac impedance in air at temperatures ranging from 400 °C to 900 °C as mentioned in this paper.
310 citations
TL;DR: In this article, the effects of the addition of small amount of rare earth cations were investigated for the suppression of hole conduction in the high oxygen partial pressure range, with La 0.8 Sr 0.2 Ga 0.
250 citations
TL;DR: In this paper, the ionic conductivity and lithium electrode-electrolyte interfacial stability have been measured for composite polymer electrolytes using micrometer-and nanometer-size alumina (Al2O3) with polyethylene oxide (PEO) and lithium tetrafluoroborate (LiBF4).
239 citations
TL;DR: In this paper, the system of lithium iodide dissolved in poly(ethylene oxide), which are prototypes of polymer electrolytes used, for example, in batteries, was studied by means of molecular dynamics simulations.
Abstract: Systems of lithium iodide dissolved in poly(ethylene oxide), which are prototypes of polymer electrolytes used, for example, in batteries were studied by means of molecular dynamics simulations. Investigations were aimed at the molecular driving force behind the salt uptake, the mechanism of ion transport, participation of the polymer in ion transport, ion clustering, change of polymer properties by the presence of ions, and ionic conductivity. Particular attention has been given to the differences in behavior between (previously studied) neutral and ionic species dissolved in polymers.
229 citations
TL;DR: In this article, the ionic conductivity data obtained for Feand Ni-doped SrTiO3 in this way are compared to data obtained from the analysis of the oxygen partial pressure dependence of the total conductivity as well as to defect chemical calculations.
Abstract: Knowledge of the exchange kinetics of O2 in SrTiO3 allows us to design appropriate strategies to separate the ionic and the electronic conductivity. In the low-temperature range, where the overall surface reaction is very slow compared to bulk diffusion and measuring time, electrochemical cells of the type Pt|SrTiO3|Pt are self-blocking and self-sealing and a Wagner–Hebb-type polarization succeeds without the necessity of using selectively blocking electrodes. In the present study the ionic conductivity data obtained for Feand Ni-doped SrTiO3 in this way are compared to data obtained from the analysis of the oxygen partial pressure dependence of the total conductivity as well as to defect chemical calculations. In complete contrast to the low temperature situation, at high temperatures, where the surface reaction is fast, the emf technique is conveniently applicable. Results are presented for Pt, O2|SrTiO3|O2, Pt cells. The conductivity behavior of SrTi(Fe)O3 as a function of temperature (20°–1000°C) is complex, due to partially frozen-in equilibria, but even details can be quantitatively understood in terms of a simple defect chemistry. The turnover of the diffusion-controlled regime to the surface reaction-controlled regime can be shifted to significantly lower temperatures by using YBa2Cu3O7–8 electrodes.
218 citations
TL;DR: In this paper, the role of the oxygen vacancies with respect to the ionic conductivity in perovskites and brownmillerite phases is discussed in detail, and the structures of these phases containing oxygen vacancies are surveyed.
207 citations
TL;DR: In this paper, the conductivity at 773 K was 2.3 × 104 S cm−1 for Nd10(SiO4)6O3 (Ln = La, Nd, Sm, Gd and Nd).
Abstract: Electrical properties were investigated for lanthanoid-silicates of Ln10(SiO4)6O3(Ln = La, Nd, Sm, Gd and Nd). The conductivity at 773 K was 2.3 × 104 S cm−1 for Nd10(SiO4)6O3. The sole carrier is the O2− ion, which was determined using an O2 gas concentration cell.
TL;DR: In this article, electrical conductivity measurements are reported on the rare earth pyrochlore compound Gd2Ti2O7 as a function of temperature, oxygen partial pressure and aliovalent dopant concentration.
TL;DR: In this article, a conduction model was proposed consistent with the aging phenomenon, which showed the importance of the supply of H2O vapor to the ambient during sintering, for the lattice hydroxide ions of ceramic HAp were considerably dehydrated.
Abstract: In the study of the high-temperature behavior of ceramic hydroxyapatite (HAp), it was found in relation to its ionic conduction properties that HAp underwent partial dehydration of its lattice hydroxide ions. Considering that HAp ceramics are sintered above 1200°C without destruction of the apatitic structure, the dehydration was interpreted as an unstable phenomenon of aging. The evolution of instability of dehydration was reflected in the time-dependent characteristics of conductivity, which exhibited up-and-down change of 103 S·cm−1 above 700°C. The conduction was proved purely protonic by measurements of a hydrogen concentration cell, and it was noted that the protonic conductivity was increased to a high value of 10−3 S·cm−1 at the initial stage of the aging. The aging phenomenon was demonstrated to be reversible in the deuteration of fully aged HAp; the uptake of OD− inside the specimen was confirmed by infrared spectroscopic analysis after exposure to deuterium oxide vapor. Based on those results, a conduction model was proposed consistent with the aging phenomenon. The present study also showed the importance of the supply of H2O vapor to the ambient during sintering, for the lattice hydroxide ions of ceramic HAp were considerably dehydrated in sintering in air at high temperatures.
TL;DR: In this paper, a novel group of polymer electrolytes based on poly(vinyl sulfone) (PVS) and polyvinylidene fluoride (PVdF) polymers, plasticized with highly conductive solutions of LiClO4, LiN(CF3SO2)2 or LiAsF6, were prepared via in situ photopolymerization and solution casting, respectively.
TL;DR: In this article, the electrical conductivity of monocrystalline (3.0, 9.5, 12.0 and 17.9 mol% yttria)-doped zirconia samples was studied using impedance spectroscopy in the temperature range of 250-1200 °C.
TL;DR: In this paper, a crystalline form of lithium phosphorus oxynitride, Li 2.88 PO 3.73 N 0.14, has been prepared by solid state reaction between Li 3 N and LiPO 3 under a flowing N 2 atmosphere.
TL;DR: In this paper, a poly(ethylene oxide)-NaPF6 polymer electrolytes have been studied by X-ray diffraction, IR, differential thermal analysis, optical microscopy, polarization, and impedance spectroscopic techniques.
Abstract: Poly(ethylene oxide)-NaPF6 polymer electrolytes have been studied by X-ray diffraction, IR, differential thermal analysis, optical microscopy, polarization, and impedance spectroscopic techniques. The material is shown to be an ionic conductor with tion ≈ 0.98, tNa+ ≈ 0.45 and tanion ≈ 0.53. The σ vs. 1 T curves show apparent Arrhenius behaviour below and above Tm.
TL;DR: In this article, the elementary steps of proton conductivity in oxides, proton transfer and hydroxyl ion reorientation, are investigated and the anticipated H D isotope effects of their rates are compared to those of Proton (deuteron) conductivity.
TL;DR: In this paper, Li0.99PO2.30 glass with σ ∼ 3.0 × 10−7 S cm−1 at 25°C and Ea = 0.60 eV was probed by X-ray photoelectron spectroscopy and high performance liquid chromatography.
Abstract: Lithium phosphorus oxynitride glasses with different lithium contents have been prepared by melting base glasses at high temperature in a flowing ammonia atmosphere for 16–72 h. The melt was then furnace-cooled to room temperature to avoid bubble formation in the sample. The structure of the lithium phosphorus oxynitride glasses was probed by X-ray photoelectron spectroscopy and high performance liquid chromatography. The results of ac impedance measurements show that nitrogen incorporation into the glass structure increases the ionic conductivity. The highest conductivity was found in Li0.99PO2.55N0.30 glass with σ ∼ 3.0 × 10−7 S cm−1 at 25°C and Ea = 0.60 eV.
TL;DR: In this paper, a defect chemistry model is proposed for brownmillerite oxides with high oxygen ion conductivity, and its electrical conductivity and transport properties have been studied in detail.
TL;DR: In this article, a number of new salts with monomer functionality and bearing a perfluorosulfonate group have been synthesized and the results in terms of ionic conductivities and thermal behavior are reported for these singlecation conductor polymer electrolytes.
TL;DR: Water-containing and anhydrous alkaline PEO-based solid polymer electrolytes have been prepared, involving two different technologies as discussed by the authors, and they exhibit a high ionic conductivity, and values up to 10−3 S cm−1 are obtained for some compositions at room temperature.
TL;DR: In this paper, the authors investigated the ion transport mechanisms at the molecular level in yttrium-stabilized zirconia and found that the conductivity of Y3+-Y3+ ion clusters trapped more O2-vacancies than did isolated Y3+, and this tendency increased with increasing Y2O3 concentration.
Abstract: The electric conductivity of yttrium-stabilized zirconia exhibits a maximum as a function of dopant (Y3+) cation concentration in isothermal and isobaric conditions. In order to improve the conductivity of this important solid electrolyte, it is essential to understand the ion transport mechanisms at the molecular level. This was investigated by the molecular dynamics simulations method in the present study. The composition dependency of the electric conductivity was found to agree qualitatively with experimental data. The conductivity was found to depend on the dopant Y3+ distribution. The O2-O2- radial distribution function showed that oxygen ions were displaced about 0.37 AA towards O2- vacancies. The radial distribution functions of cations showed that the local structural environment of Y3+ ions was more disordered than that of the Zr4+ ions. Oxygen vacancies were found to be nearest neighbours of Y3+ ions. The Y3+-Y3+ neighbour clusters trapped more O2- vacancies than did isolated Y3+ ions, and this tendency increased with increasing Y2O3 concentration in ZrO2 because more and larger Y3+-Y3+ clusters were formed. We suggest that this is responsible for the observed isothermal conductivity decrease at high Y2O3 contents in the yttrium-stabilized zirconia.
TL;DR: A model for the oxygen flow density through the mixed conductor caused by chemical potential gradient is proposed in this article. But it is not shown that oxygen permeability decreases in the La > Pr > Nd sequence.
TL;DR: In this article, the crystal structures of PEO 3 -LiCF 3 SO 3, PEO 4 -NaClO 4, KSCN and RbSCN were studied and the importance of intrachain rather than interchain cross-linking was highlighted.
TL;DR: In this article, the stoichiometry, stability and polymorphism of perovskite-related solid solutions, Li0.5 +xTiO3: RELa, Nd, has been studied.
Abstract: The stoichiometry, stability and polymorphism of the perovskite-related solid solutions, Li0.5 – 3xRE0.5 +xTiO3: RELa, Nd, has been studied. For both series, the data are presented in the form of a temperature vs. composition phase diagram. Unit cell data for the different polymorphs (three in the La system, four in the Nd system) are presented, together with data on the composition and thermal history dependence of the lattice parameters. The phase composition and microstructure of selected ceramic samples were analysed by electron microprobe techniques.
TL;DR: The highest ionic conductivity was observed in Bi 4 V 1.70 Ti 0.30 O 10.85 with σ 500 k = 4 × 10 −4 S/cm as discussed by the authors.
TL;DR: In this article, a dielectric ceramics of the system (Ba,Ca,Ti,Zr)O3 (BCTZ) have been fired with BaO-excess in reducive atmosphere.
Abstract: Dielectric ceramics of the system (Ba,Ca)(Ti,Zr)O3 (BCTZ) have been fired with BaO-excess in reducive atmosphere. By the influence of BaO-excess the Ca2+-ions are shifted from the Ba- to the Ti-sites of the perovskite lattice. The solubility of Ca2+ on Ti-sites is largely independent of the firing atmosphere, but shows a pronounced temperature dependence. At 1400 °C ≅ 2 at.% Ca can be dissolved on the Ti-sites. Ca-ions on Ti-sites are strong electron acceptors. Highly insulating materials can be thus prepared in reducive atmospheres. The Ca-acceptors are electrically compensated by large numbers of ionized oxygen vacancies. Electromigration of the oxygen vacancies gives rise to ionic conductivity, resulting in low life stability of multilayer capacitors, sintered in reducive atmosphere.
TL;DR: In this article, a molecular dynamics simulation technique was used to investigate the oxygen tracer diffusion in the oxygen ionic conductor yttria-stabilized zirconia.