Showing papers on "Ionic conductivity published in 1974"
TL;DR: The growth of calcium oxalate monohydrate crystals in stirred suspensions has been studied by following the changes in ionic conductivity in supersaturated solutions containing both stoichiometric and non-stochastic concentrations of lattice ions at various temperatures in the range 15-45 °C as discussed by the authors.
171 citations
TL;DR: In this article, the electrical conductivity and ion/electron transference numbers in Al3O3 were determined in a sample configuration designed to eliminate influences of surface and gas-phase conduction on the bulk behavior.
Abstract: The electrical conductivity and ion/electron transference numbers in Al3O3 were determined in a sample configuration designed to eliminate influences of surface and gas-phase conduction on the bulk behavior. With decreasing O2 partial pressure over single-crystal Al2O3 at 1000° to 1650°C, the conductivity decreased, then remained constant, and finally increased when strongly reducing atmospheres were attained. The intermediate flat region became dominant at the lower temperatures. The emf measurements showed predominantly ionic conduction in the flat region; the electronic conduction state is exhibited in the branches of both ends. In pure O2 (1 atm) the conductivity above 1400°C was σ≃3×103 exp (–80 kcal/RT) Ω−1 cm−1, which corresponds to electronic conductivity. Below 1400°C, the activation energy was <57 kcal, corresponding to an extrinsic ionic condition. Polycrystalline samples of both undoped hot-pressed Al2O3 and MgO-doped Al2O3 showed significantly higher conductivity because of additional electronic conduction in the grain boundaries. The gas-phase conduction above 1200°C increased drastically with decreasing O2 partial pressure (below 10−10 atm).
78 citations
TL;DR: In this paper, the dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 20 Hz to 1 MHz and between 100 and 220°C, during heating and cooling.
Abstract: Dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 20 Hz to 1 MHz and between 100 and 220°C, during heating and cooling. The dielectric constant and loss change abruptly at the temperature Tm corresponding to the melting point. At lower frequencies, two types of ionic conductin are observed. One appears below Tm and is attributed to interfacial polarization. The other occurs above Tm and is related to electrode polarization. These results suggest that a crystalline polymer is a heterogeneous medium for ionic transport, while the melt is a homogeneous medium. From these results, the nature of ac ionic conduction in crystalline polymers is discussed. At high frequency, the α relaxation is observed below Tm. It is due to the molecular motion in the crystalline region and disappears at Tm.
46 citations
TL;DR: In this paper, the space charge conductance and bulk conductivity of epitaxial {111} and {200} films of AgCl with thickness in the 1-μ range was measured.
40 citations
01 Apr 1974-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: The electrical conductivity of solid calcium sulfide has been measured at various temperatures and sulfur pressures with the aid of an alternating current bridge as mentioned in this paper, showing that the conduction is predominantly ionic for sulfur pressures less than about 10−6 atm.
Abstract: The electrical conductivity of solid calcium sulfide has been measured at various temperatures and sulfur pressures with the aid of an alternating current bridge. At partial pressures less than about 10−6 atm at 770°C to 1000°C, the conductivity is independent of sulfur pressure and can be expressed by log10 σ (Ω−1 ·cm−1) = −5.185/T(K) − 0.0901 The apparent activation energy for the conduction is 23.7 (± 1.04) kilocalories per mole. Both the relatively large activation energy and the lack of dependence of the specific conductivity on sulfur pressure suggest that the conduction is predominantly ionic for sulfur pressures less than about 10−6 atm. However, for pressures greater than 10−6 atm, the specific conductivity increases with an increase of the sulfur pressure, suggesting positive hole conduction. Some comments are included on the possibility of the application of calcium sulfide as a solid electrolyte of a sulfur concentration cell.
32 citations
TL;DR: In this paper, the electronic and ionic conductivities of ZrO/sub 2/ were determined as a function of temperature, oxygen partial pressure, and trivalent dopant content.
Abstract: The electronic and ionic conductivities of ZrO/sub 2/ were determined as a function of temperature, oxygen partial pressure, and trivalent dopant content. Observations were in reasonable agreement with the proposed defect structure model. Ionic conductivity for undoped zirconia was attributed to doubly ionized oxygen interstitials at high oxygen pressures and to doubly ionized oxygen vacancies at the lower extreme of the oxygen partial pressure. Doped zirconia, contrary to the undoped sample, showed maximum ionic transport at intermediate oxygen pressures. The ionic conductivity, due to extrinsic dopant effects, increased by increasing the amount of dopant and its range extended over a wider oxygen partial pressure. The observed decrease in activation energy for ionic condnctivity upon doping was attributed to the formation of anion vacancies whose concentration is directly proportional to the dopant contert. The 1 mole percent Y/sub 2/O/sub 3/ sample showed predominant ionic transport. (13 figures, 24 references) (auth)
31 citations
TL;DR: In this paper, the mixed conductivity (ionic and electronic) of Ag2S was measured at room temperature by a square wave method and it was estimated that the exchange current density is at least 100 mA cm2 for a 0·1 M AgNO3 solution.
29 citations
TL;DR: BaCl2 and SrBr2 transform at 1193 K and 918 K respectively to highly conducting (solid electrolyte) phases with an increase of ionic conductivity of several orders of magnitude as discussed by the authors.
26 citations
TL;DR: In this article, the effects of various dyes upon the electrical conductivity of cubic silver bromide grains with edge lengths of 0.9 μm in a photographic emulsion have been studied with the aid of dielectric loss measurements.
Abstract: The effects of various dyes upon the electrical conductivity of cubic silver bromide grains with edge lengths of 0.9 μm in a photographic emulsion have been studied with the aid of dielectric loss measurements. The conductivity of the grains was increased by 3,3′‐diethyl‐9‐methylthiacarbocyanine bromide (dye 1) and 1,1′‐diethyl–2,2′‐quinocyanine iodide (dye 2), and decreased by erythrosin (dye 3) and a merocyanine (dye 4). Based on the knowledge that dyes 1 and 2 are tightly attached to positively charged surface sites composed of silver ions, and that dyes 3 and 4 to negatively charged surface sites, the results are considered to provide evidence for the view on the formation of interstitial silver ions through the positively charged surface sites on silver bromide microcrystals.
25 citations
TL;DR: In this article, the authors investigated the kinetics of selenization of silver by liquid selenium, the Ag/Ag2Se interface reaction rate, the ionic conductivity of Ag+ in Ag2Se layer, and the over-all reaction rate were determined.
Abstract: In order to elucidate the kinetics of selenization of silver by liquid selenium, the Ag/Ag2Se interface reaction rate, the ionic conductivity of Ag+ in Ag2Se layer, the Ag2Se/Se(1) interface reaction rate, and the over-all reaction rate were determined. The Ag/Ag2Se interface reaction rate was found to be given by υ=1.6×10^9{exp(-32300/RT)}(a_Se) eqv cm^-2·s^-1 The following mechanism was proposed for the interface reaction. 2Ag(Ag)+Se(Ag_2Se)→2Ag^+(Ag_2Se)+Se^2-(Ag_2Se) It was found that the driving force of the Ag2Se/Se(1) interface reaction is very small and Ag2Se is in equilibrium with Se(1). On an assumption that the over-all reaction is controlled by both the Ag/Ag2Se interface reaction and the diffusion of Ag+ in Ag2Se, the over-all reaction rates were calculated. The results agree with the observed ones.
20 citations
TL;DR: In this article, the chemical interdiffusion via a pure vacancy mechanism is treated both in binary ionic solid solutions and metal alloys of cubic structure in the case of variable partial molar volumes.
Abstract: Chemical interdiffusion via a pure vacancy mechanism is treated both in binary ionic solid solutions and metal alloys of cubic structure in the case of variable partial molar volumes. Both phenomenological and kinetic theories are used. Expressions for the chemical diffusion coefficient and the Kirkendall velocity are derived. Also expressions for the ionic conductivity, the diffusion field and the shift of tracer profile are derived. The results are discussed for KCl-RbCl, TlCl-TlBr, CoO-NiO, Fe-Ni, Cu-Ni, Au-Ni, Co-Pd and Cu-Ag systems.
TL;DR: In this paper, the authors investigated polycrystalline BaTiO 3 in the presence of water vapor and showed that the transference number of ions within the electrolyte increased with higher water vapor concentrations in the anode compartment of the cell.
TL;DR: In this paper, a comparison of the heterogeneous catalytic activities of ZrO2, Zr0.91Ca0.09O1.91 and Th0.85La0.15O 1.925 for the oxidation of CO by O2 was made.
Abstract: A comparison is made of the heterogeneous catalytic activities of ZrO2, Zr0.91Ca0.09O1.91 and Th0.85La0.15O1.925 for the oxidation of CO by O2. A correlation is evident with the magnitudes of the simultaneous bulk ionic and electronic conductivities. This is in accord with a postulated model for reaction at separate reactant absorption sites in which oxygen ions and electronic charge are transported in and on the surface of the oxide catalyst.
TL;DR: In this paper, the dielectric behavior of cerium dioxide with calcium concentrations ranging up to 8 mole % was investigated from 50 to 600 kHz and from room temperature to 1000 deg C.
Abstract: The dielectric behavior of cerium dioxide with calcium concentrations ranging up to 8 mole % were investigated from 50 to 600 kHz and from room temperature to 1000 deg C. At temperatures less than 500 deg C and calcium concentrations less than 1.0 mole %, barrier layer polarization seemed responsible for the observed dielectric behavior. At larger calcium concentrations and higher temperatures, where ionic conduction predominated, the dielectric behavior was rationalized on the basis of a space charge polarization model involving mobile ionic point defects, which were blocked or partially blocked at the specimen electrodes, and electronic carriers, which were able to freely pass through the electrodes. The effective dielectric constant was found to increase exponentially with temperature with an activation energy of approximately 0.74 eV.
TL;DR: In this paper, a vacancy mechanism involving both anions and cations is proposed to explain the results of ionic transport in NH 4 Cl −, where the anions are replaced by cations.
TL;DR: In this article, the ionic conductivity and self-diffusion of chlorine ions in undoped single crystals of zone-refined lead chloride have been measured over the temperature range 625-370K.
Abstract: The ionic conductivity and self-diffusion of chlorine ions in undoped single crystals of zone-refined lead chloride have been measured over the temperature range 625–370K. These measurements suggest that the conductivity and self-diffusion are due to simple vacancy migration as confirmed by the observed correlation factor. The activation energy of formation of vacancies is found to be 1.55 eV and that for migration of an anion is 0.38 eV. In the extrinsic region, the two measurements show marked discrepancies which are explained by assuming the presence of oxygen impurity ions in the lattice, and the mechanisms for their contribution to the observed excess conductivity are discussed.
TL;DR: In this paper, the individual ionic activity coefficients of strong electrolytes in dilute aqueous solutions are derived from the ionic conductivity data, using the Debye-Huckel-Onsager theory of the strong electrolyte solutions.
Abstract: The individual ionic activity coefficients of strong electrolytes in dilute aqueous solutions are derived from the ionic conductivity data, using the Debye-Huckel-Onsager theory of strong electrolyte solutions. The mean activity coefficients computed by the present method are in good agreement with the experimental values in most of the uni-univalent and some of the uni-multivalent electrolytes studied, which demonstrates the validity of the method in deriving the individual ionic activity coefficients. Comparisons are made of the values of individual activity coefficients of various ions in dilute aqueous solutions of strong electrolytes, as determined by different methods including measurements of potential differences across membranes at varying concentrations. The influence of the ion of opposite sign on the individual ionic activity coefficient has been observed.
TL;DR: In this article, the energy of formation of Schottky defects as well as cation and anion migration energies in RbCl, RbBr and RbI have been evaluated from ionic lattice calculations.
Abstract: Energies of formation of Schottky defects as well as cation and anion migration energies in RbCl, RbBr and RbI have been evaluated from ionic lattice calculations and the results are compared with the corresponding values obtained from ionic conductivity measurements. The experimental and calculated values of Schottky formation energies agree. Conduction in rubidium halides is mainly due to the movement of cation vacancies. The calculated value of the cation migration energy in RbCl is close to that obtained experimentally, but the calculated values in RbBr and RbI are somewhat higher than the experimental values.
Patent•
09 Sep 1974
TL;DR: In this paper, a temperature programmable charge storage device is provided having dielectric material composed of an ionic solid doped with a dominant impurity, interposed between two electrodes of electrical conductivity less than the ionic conductivity of the doped dielectrics.
Abstract: A temperature programmable charge storage device is provided having dielectric material composed of an ionic solid doped with a dominant impurity. The dielectric is interposed between two electrodes of electrical conductivity less than the ionic conductivity of the doped dielectric and means are provided for heating the dielectric to program the charge-discharge rate of the device.
01 Dec 1974
TL;DR: In this article, it was shown that the conductivity of cellulose in vacuo increases rapidly with voltage gradient; it is given by a sum of two exponential terms, i.e., (dlnσ/dV)kTe−1, where g is the width of the gap, σ the conductivities, k Boltzmann's constant, T the temperature in °K, and e the electronic charge.
Abstract: It is shown that the conductivity of native cellulose in vacuo increases rapidly with voltage gradient; it is given by a sum of two exponential terms. While the conductivity of this material is ionic, as evidenced by the development of H2 in approximate agreement with Faraday's law, it is proposed that the increase of conductivity with voltage is caused by local electronic conduction in transient thermally-generated defects in the form of voids. These defects have essentially the same basis in statistical mechanics as the defects on which the theory of ionic conduction in crystals is based (Frenkel and Schotky defects); they should be present in a concentration proportional to a Boltzmann factor. They give mobility to the ions generated by the thermal dissociation of the molecules. In order to explain the voltage dependence it is proposed that negative ions tend to collect in small excess on one side of a defect or gap and positive on the other. The unoccupied levels in the positive ions are above the occupied levels in the negative ions, but when an adequate electric field is applied they can be brought into coincidence, and wave-mechanical transport of an electron occurs, as in the Gurney theory of electrolysis. Developing this quantitatively leads to the relation g = (dlnσ/dV)kTe−1, where g is the width of the gap, σ the conductivity, k Boltzmann's constant, T the temperature in °K, and e the electronic charge. The values of g calculated from the data cluster around two mean values: g = 19.5A and g = 34.9A, the first corresponding to the higher, the second to the lower part of the range of voltage gradients. This model indicates that H2 and O2 should be generated in the defects or voids by this type of internal electrolysis. Experimentally H2 and CO are generated at a rate increasing with voltage, such that at 0.5 × 106 V/cm the yield is about 2 moles/f, i.e., too large for an electrode effect. Thus the model explains both the voltage-dependence of conductivity and that of the electrochemical yield (of H2), using properties already needed for the explanation of conduction and electrolysis. The presence of transient defects (or voids) in thermodynamic equilibrium can also be used in the model for the explanation of the conductivity/water-content relationship. It is proposed that the conductivity is proportional to the probability of simultaneous adsorption of single water molecules at nine discrete sites, characteristic of each transient defect.
TL;DR: In this article, the additive properties of the Na2O-Fe2O3-P2O5 system were studied over the temperature range 20°-180°C.
Abstract: The electrical conduction and dielectric relaxation of some glasses in the system Na2O-Fe2O3-P2O5 were studied over the temperature range 20°-180°C. This system contains Na2O which confers an ionic conductivity on glass and Fe2O3 an electronic conductivity.The conductivity of this kind of glass may be expected to have an additive property from which it can be calculated by the addition of ionic and electronic conduction. In this study the experimental results were discussed in view of the additive property. Samples used in this experiment were prepared by melting under different conditions, i.e. in the air and in a reducing atmosphere. The ratio (Fe2+/Fe2++Fe3+) in the glass was determined by chemical analysis. The conductivity was observed to vary greatly with the melting temperature. The values of log σ increase with increasing Fe2+ ion in the glasses of compositions 40Fe2O3-60P2O5, 10Na2O-30Fe2O3-60P2O5, 20Na2O-20Fe2O3-60P2O5; but on the contrary in the galss containing relatively small amount of Fe2O3, 30Na2O-10Fe2O3-60P2O5, the log σ decreases with increasing Fe2+ ion. This can be considered from the fact that the mechanism of hopping theory holds for the glass containing a large amount of Fe2O3 and does not hold for the glass with small amount of Fe2O3 content. The d.c. conductivity (σ) of glasses of the formula xNa2O-(40-x)Fe2O360P2O5 was shown by replacing Fe2O3 with Na2O to have a minimum value at the composition near x=20 at temperature above 100°C, but at temperature below 100°C the x-value showing the minimum conductivity was seemed to shift toward its higher value. The activation energies ΔHdc and ΔHac were found to be grouped into two parts, the higher values in the compositions near (40Na2O-60P2O5) in which ionic conduction predominate and the lower values in the compositions near (40Fe2O3-60P2O5) in which electronic conduction predominate.The dielectric relaxation was observed by changing frequency and temperature. The values of dielectric constant e′ and dielectric absorption e″ were measured in glasses melted by various conditions.The normalized dielectric losses at various temperature was shown by plotting e″/e″max against log (f/fmax) but it was independent of temperature. The relationship between σ and the frequency at which the dielectric loss becomes maximum, fmax, was found to follow the equation proposed by H. Namikawa.
TL;DR: In this article, a simplified equation for the activation energy was derived in which the dependence of the electric field on ionic jump energy and ionic dissociation energy was taken into consideration.
Abstract: Electrical conduction of poly (methyl methacrylate) (PMMA) is considered to be ionic from low to very high fields near breakdown. Support for the ionic mechanism can be supplied from the compensation law, and from the temperature dependence of the electrical conductivity and the breakdown field. In high electric fields above the ohmic region, it was observed that the apparent activation energy decreased with increasing electric field. A simplified equation for the activation energy was derived in which the dependence of the electric field on ionic jump energy and ionic dissociation energy was taken into consideration. The ionic jump distance between equilibrium positions computed from the equation was 10 to 20 A and was in good agreement with periodic structure of PMMA.
TL;DR: In this paper, the electrical conductivity and ion/electron transference numbers in Al3O3 were determined in a sample configuration designed to eliminate influences of surface and gas-phase conduction on the bulk behavior.
Abstract: The electrical conductivity and ion/electron transference numbers in Al3O3 were determined in a sample configuration designed to eliminate influences of surface and gas-phase conduction on the bulk behavior. With decreasing O2 partial pressure over single-crystal Al2O3 at 1000° to 1650°C, the conductivity decreased, then remained constant, and finally increased when strongly reducing atmospheres were attained. The intermediate flat region became dominant at the lower temperatures. The emf measurements showed predominantly ionic conduction in the flat region; the electronic conduction state is exhibited in the branches of both ends. In pure O2 (1 atm) the conductivity above 1400°C was σ≃3×103 exp (–80 kcal/RT) Ω−1 cm−1, which corresponds to electronic conductivity. Below 1400°C, the activation energy was <57 kcal, corresponding to an extrinsic ionic condition. Polycrystalline samples of both undoped hot-pressed Al2O3 and MgO-doped Al2O3 showed significantly higher conductivity because of additional electronic conduction in the grain boundaries. The gas-phase conduction above 1200°C increased drastically with decreasing O2 partial pressure (below 10−10 atm).
TL;DR: In this article, electrical conductivity of crosslinked poly-4-vinylmethylpyridinium electrolytes in the film form has been measured as a function of temperature from −50°C to + 150°C.
TL;DR: In this article, the authors examined crystal growth from the aqueous solution for KCl and KI and suggested that concentrations of impurities are, in general, lower in solution-grown crystals than in melt-grown.
Abstract: Crystal growth from the aqueous solution was examined for KCl and KI. By a gradual decrease of the temperature of the solution, new crystal layers are grown onto a seed and they attain a thickness up to a few millimeters in the course of several weeks. The ultra-violet absorption of as-grown crystals gives no indication of the incorporation of OH- ions, and the F-band which is induced by X-ray irradiation at room temperature scarcely shows the distinction between the first and second stages of coloration. Along with the ionic conductivity of crystals and the additive coloration by alkali metals, it is suggested that concentrations of impurities are, in general, lower in solution-grown crystals than in melt-grown crystals.
TL;DR: In this article, the radiation-induced ionic polymerization of α-methylstyrene has been studied by means of the Hittorf type conductivity measurement, and it was concluded that freely moving electrons play an important role in the polymerization.
Abstract: The radiation-induced ionic polymerization of α-methylstyrene has been studied by means of the Hittorf type conductivity measurement. For extremely dry samples it has been estimated that the chain transfer to monomer is about 105. It was concluded that freely moving electrons play an important role in the polymerization.
01 Jan 1974
TL;DR: In this article, large values of cationic conductivity have been found in some solid oxides at relatively low temperatures, which is related to the presence of crystallographic tunnels within which certain ions can be very mobile.
Abstract: Unusually large values of cationic conductivity have recently been found in some solid oxides at relatively low temperatures. This behavior is related to the presence of crystallographic tunnels within which certain ions can be very mobile.
TL;DR: In this paper, the authors describe a scenario in which a group of people are living in a large, chaotic, and inhospitable environment, and they describe the following behaviors:
Abstract: 弗化カルシウムの焼結において, 原料粉末に吸着している水分の影響を調べた. 単にアルゴン中で焼結した場合と, 水分を除去しつつ減圧下で焼結した場合とを比較した. この結果, 水の存在は, 焼結組織および焼結体のイオン伝導度に大きな影響を及ぼしていることが認められた. 酸素をドープした単結晶の伝導度との比較から, 水は弗化カルシウムと反応し, 弗素空孔を生じていると結論された.
TL;DR: In this paper, the individual ionic activity coefficients of strong electrolytes in dilute aqueous solutions are derived from the ionic conductivity data, using the Debye-Huckel-Onsager theory of the strong electrolyte solutions.
Abstract: The individual ionic activity coefficients of strong electrolytes in dilute aqueous solutions are derived from the ionic conductivity data, using the Debye-Huckel-Onsager theory of strong electrolyte solutions. The mean activity coefficients computed by the present method are in good agreement with the experimental values in most of the uni-univalent and some of the uni-multivalent electrolytes studied, which demonstrates the validity of the method in deriving the individual ionic activity coefficients. Comparisons are made of the values of individual activity coefficients of various ions in dilute aqueous solutions of strong electrolytes, as determined by different methods including measurements of potential differences across membranes at varying concentrations. The influence of the ion of opposite sign on the individual ionic activity coefficient has been observed.