Dc Ionic Conductivity Research Articles

Effects of preparation methods on structure, ionic conductivity and dielectric relaxation of solid polymeric electrolytes

The solid polymer electrolytes (SPEs) consisted of poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO4) (PEO20–LiClO4 and PEO8–LiClO4 electrolytes of composition stoichiometric ratios EO:Li+ = 20:1 and 8:1) have been prepared by various blending methods. The simple solution casting, solution–cast hot pressed, dry blended melt pressed, high intensity ultrasonic assisted, microwave irradiated, and both the ultrasonicated and microwave irradiated solution–cast followed by their remelt with hot pressed methods have been used for preparation of the SPEs films. The complex formation between etheric oxygen (EO) of PEO and cation (Li+) of LiClO4 is confirmed by relative changes in amorphous phase of these electrolytes which is investigated by X-ray diffraction measurements. It is found that the amount of amorphous phase of these SPEs is strongly influenced by their preparation methods and the salt concentration. The complex dielectric function, ac electric conductivity, electric modulus and impedance spectra of the electrolytes are studied over the frequency range of 20 Hz to 1 MHz by dielectric relaxation spectroscopy at ambient temperature. The dc ionic conductivity of PEO8–LiClO4 electrolytes is found two to three orders of magnitude higher than that of the PEO20–LiClO4 electrolytes, which is significantly affected by their preparation methods. The cations coupled PEO chain segmental dynamics and its correlation with the ionic conductivity of these electrolytes has been explored by considering the values of relaxation times and dielectric relaxation strength. Results reveal that the ionic conductivity of PEO8–LiClO4 electrolytes can be tuned over two orders of magnitude by adopting different blending methods with a state-of-the-art engineering.

Influence of chromium content on the optical and electrical properties of Li1+xCrxTi2−x(PO4)3

Abstract Optical and electrical properties of samples with Li 1 + x Cr x Ti 2 − x (PO 4 ) 3 composition ( x = 0, 0.05 and 0.1) prepared by a low temperature sol-gel method have been investigated. XRD and Raman spectroscopy measurements respectively reveal the rhombohedral-Nasicon structure of the grown samples and a disorder of Li + ions with increasing chromium content. Electrical properties were studied by impedance spectroscopy and both dc and grain boundary ionic conductivity increase with Cr content. A high ionic conductivity value of 1.4·10 − 4 S cm − 1 at room temperature and an activation energy of 0.31 eV have been obtained for x = 0.1, which are comparable to those measured in the best ionic conductors reported to date. Photoluminescence and cathodoluminescence spectra indicate that self-trapped excitons and oxygen defects related to the TiO 6 octahedra structural units are responsible for the observed luminescence in the visible spectral range, explaining the possible electronic origin of a residual conductivity measured in all the samples. Cr incorporation gives rise to infrared emission bands, attributed to different Cr 3 + and Ti 3 + intraionic transitions, that may be related to the better grain connectivity achieved by Cr doping.

Ionic conductivity in a quantum lattice gas model with three-particle interactions

A system of mesoscopic ions with dominant three-particle interactions is modeled by a quantum lattice liquid on the planar kagomé lattice. The two-parameter Hamiltonian contains localized attractive triplet interactions as potential energy and nearest neighbor hopping-type terms as kinetic energy. The dynamic ionic conductivity σ(ω) is theoretically investigated for ‘weak hopping’ via a quantum many-body perturbation expansion of the thermal (Matsubara) Green function (current-current correlation). A simple analytic continuation and mapping of the thermal Green function provide the temporal Fourier transform of the physical retarded Green function in the Kubo formula. Substituting pertinent exact solutions for static multi-particle correlations known from previous work, Arrhenius relations are revealed in zeroth-order approximation for the dc ionic conductivity σdc along special trajectories in density–temperature space. The Arrhenius plots directly yield static activation energies along the latter loci. Experimental possibilities relating to σdc are discussed in the presence of equilibrium aggregation.This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

Low-Temperature DC Conductivity of LiNbO3 Single Crystals

Abstract We report on conductivity measurements of LiNbO3 single crystals with congruent composition in ambient atmosphere between 449 and 727 K which include the lowest temperatures covered so far. The ionic DC conductivity observed along the c-axis at, e. g., 650 K is 6.7 × 10-9 S/cm and shows an activation energy of 1.33 eV. The corresponding Li + diffusion coefficients range between 2.5 × 10-22 and 1.4 × 10-16 m2/s. These results are perfectly consistent with our conductivity results in the high-temperature regime as well as SIMS measurements published recently (Rahn et al., Phys. Chem. Chem. Phys. 14 (2012) 2427). From the Li + diffusion coefficients obtained here a Haven ratio of 0.7(2) can be deduced.

Temperature Behavior of Electric Relaxational Effects due to Ionic Conductivity in Liquid Lactones

This paper concerns the studies of temperature and frequency behavior of the complex impedance, electric modulus, and electric conductivity due to an ionic current in liquid γ-butyrolactone (GBL) and γ-valerolactone (GVL). The frequency of the applied electric stimulus (500 Hz to 5 MHz) corresponds to the static dielectric regime of the lactones. The studies were performed in the temperature range of 263 K to 313 K. It was shown that in the static dielectric case, the dc ionic conductivity (σDC) and the static dielectric permittivity \({(\varepsilon_{\rm s})}\) determine the relaxational behavior of the impedance (Z*) and the electric modulus (M*) of the molecular liquids and both spectra are of the Debye-type characterized by the same conductivity relaxation time (τσ). Both σDC and τσ of GBL and GVL fairly well fulfill an Arrhenius temperature dependence with very similar values of the thermal activation energy \({{\rm E}_{\sigma_{\rm DC}} \approx {\rm E}_{\tau_\sigma} \approx 25 \,{\rm kJ} \, . \, {\rm mol}^{-1}}\) . The temperature dependence of the static dielectric permittivity and its temperature derivative is analyzed and interpreted in terms of the dipolar aggregation in the studied lactones.

Effect of different anions of lithium salt and MMT nanofiller on ion conduction in melt-compounded PEO–LiX–MMT electrolytes

Polymer nanocomposite electrolyte (PNCE) films composed of poly(ethylene oxide) (PEO), lithium salt (\( {\text{LiX}};\;{\text{X}} = ClO_4^{ - },\;BF_4^{ - },\;C{F_3}SO_3^{ - } \)) and montmorillonite (MMT) clay as nanofiller were prepared by melt-compounded hot-pressed technique at 70 °C under 3 tons of pressure. The ionic conductivity and relaxation behaviour of the films were investigated by dielectric relaxation spectroscopy in the frequency range of 20 Hz to 1 MHz at ambient temperature. The results revealed that the ionic conductivity of the PNCE films having 20:1 stoichiometric ratio of ethylene oxide monomer units to the lithium cation are governed by the size of different anions and the dissociation constant of salt, and also MMT concentration. It was found that PEO–LiBF4 film has comparative high dc ionic conductivity, whereas both the LiBF4 and LiClO4 containing PNCE films exhibit anomalous conductivity behaviour with varying MMT concentration. The PEO–LiCF3SO3 film has two orders of magnitude low value of dc ionic conductivity as compared to that of the other salts electrolyte films, but its conductivity enhances by one order of magnitude when 2 wt.% MMT is added as filler. A correlation between the values of ionic conductivity, conductivity relaxation time and the real part of permittivity at 1 MHz were found and the same was discussed in relation to the transient ion-dipolar type cross-linked structural behaviour of the polymeric nanocomposite electrolytes.

Investigation of ionic conductivity in track‐etched nanoporous polyimide membranes using a microwave technique

AbstractThe in situ characterization of membranes for fuel cell applications is a rather complex and time‐consuming procedure. It is therefore interesting to develop simple, short, and reproducible characterization tests and to limit in situ measurement only to the most promising materials. In this paper, a new characterization method is proposed to extract the DC ionic conductivity of track‐etched nanoporous polyimide membranes from microwave measurements. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26163

On Intermolecular Dipolar Coupling in Two Strongly Polar Liquids: Dimethyl Sulfoxide and Acetonitrile

The paper presents the results of studies of the electric and dielectric properties of dimethyl sulfoxide (DMSO) and acetonitrile (ACN), two strongly polar liquids composed of the molecules of the same dipole moment value (μ ≈ 4 D) but of a quite different static dielectric permittivity (ε(S)(DMSO) >> ε(S)(ACN)). It was shown that the activation energies for both the dc ionic conductivity (σ(DC)) and the viscosity (η) are two times higher for DMSO than for ACN; however, for both of the liquids, the temperature dependence of the product σ(DC)η is quite close to the prediction of the Stokes-Einstein relation. The dielectric results are interpreted in terms of the intermolecular dipole-dipole coupling. An exceptional behavior of DMSO most certainly results from its "monomolecularity", i.e., from the lack of the dipolar coupling in that strongly polar liquid. The effect is a consequence of a very specific structure of the DMSO molecule where its rotational dynamics makes the intermolecular dipole-dipole coupling very unfavorable, in contrast to the ACN molecules.

Non-Arrhenian Ionic dc Conductivity of Homoionic Alkali Exchanged Montmorillonites with Low Water Loadings

Dc conductivity of the whole series of homoionic alkali exchanged montmorillonites is investigated by means of Complex Impedance Spectroscopy. Conductivity of the samples is measured at the dry state and at various water loadings between 0 and 6 absorbed water molecules per cation. Dc conductivity of all the dehydrated samples follows an Arrhenius behavior. In contrast, the hydrated samples exhibit a non-Arrhenius temperature dependence of dc conductivity that is fruitfully fitted by using the VTF’s empirical law. It is then shown that the critical temperature, TVTF, increases with water loading until the later equals approximately 3 for the Li+ and Na+ samples and higher values for the K+, Rb+, and Cs+ samples. So, it appears that the departure from the Arrhenius behavior is directly related to the number of water molecules in interaction with the alkali extra-framework cations. For water loadings higher than 3, activation energy for dc conductivity tends to values of about 0.2−0.3 eV for all samples ind...

Proton transport in doped La-metaphosphate glasses

The electrical properties of [La (1 − x) M x ]–P 3O 9 metaphosphate glasses, where M is Ba, Sr, Ca, and 0 ≤ x ≤ 0.8 were investigated in the 300–500 °C range. The protonic conductivity increases two orders of magnitude from the unsubstituted to the 60% substituted glass reaching a maximum conductivity of about 10 − 5 S/cm at 450 °C. The activation energy is found to be approximately independent of concentration though dependent on the type of modifying substitutional cation, and decreases from about 1.04 eV for Ca and Sr to ∼ 0.96 eV for Ba. AC impedance measurements were used to find the DC ionic conductivities. Mean ion travel distances at the frequencies, ν Ζ * or ν Μ *, associated with the maximum in Z″ or M″ were found to be up to 30 times larger than the average oxygen spacing in the glasses. While diffusion coefficients derived from conductivities, D σ , were vastly lower than an uncorrelated diffusion coefficient computed from first principles, the travel distance at ν Z * or ν Z * derived from a simple random walk expression using D Γ , was surprisingly close to those derived from the more rigorous statistical treatments. The ratio ξ = D σ / D Γ ≪ 1 may be interpreted as indicative of highly correlated ion motion and strongly reduced mean attempt frequencies, together with a mean activation energy for motion increased by Δ E = E σ − E Γ over that of the uncorrelated intertetrahedral motion of an ideal crystal characterized by D Γ .

Novel Dynamics of Superionic Conducting Glasses Proved by Inelastic Neutron Scattering

The low-energy dynamics of Ag-based superionic conducting glass system has been investigated using the inelastic neutron scattering measurements. A clear correlation between the intensity in low-energy region and the dc ionic conductivity was found. The cross-linking factor is considered to be the network expansion by salt doping. Detailed investigations of low-energy dynamics both for varied superionic conducting glasses and insulator glass have proved that the peculiar Q dynamics beyond around 2 A -1 is a characteristic feature only in superionic conducting glass.

DC conductivity and dielectric properties in silver chloride, revisited

The anomolous DC ionic conductivity of silver chloride at high temperatures is analyzed quantitatively with the aid of mean field models and classical Monte Carlo simulations. It is found that the conductivity anomaly in silver chloride along with the exponential increase of the dielectric constant at high temperatures may be explained by referring to the idea of a "soft lattice", wherein silver ions are increasingly free to move about their regular lattice sites as the temperature rises. This wide ranging of silver ions leads to the formation of transient dipoles, which have the dual effect of increasing the dielectric constant and decreasing the free energy of the lattice.

Thermal expansion of silver iodide-silver molybdate glasses at low temperatures

Ionic glasses obtained combining silver iodide and silver molybdate are characterized by quite low values of the glass transition temperature T(g) around 320-350 K, by high values of the dc ionic conductivity even at room temperature and by a peculiar behavior of the mechanical response at ultrasonic frequencies. In fact, at temperatures well below their glass transition temperature, these glasses exhibit an intense peak of acoustic attenuation well described by two different and almost overlapping relaxational contributions. Considering also that negative thermal expansion has been reported for some molybdate crystalline compounds, we have investigated in this work the thermal expansion of two silver iodomolybdate glasses (AgI)(1-x)(Ag(2)MoO(4))(x) for x=0.25 and x=0.33 in a wide temperature range (4.2-300 K) from cryogenic temperatures up to some 20 K below T(g) using a precision capacitance dilatometer aiming to understand whether the expansivity shows some possible fingerprint corresponding to the above-mentioned mechanical response. Two different measuring methods, a quasiadiabatic and a continuous one, have been used for the thermal expansion measurements. The results are discussed in comparison with the information obtained from previous investigations based on the extended x-ray absorption fine structure (EXAFS) technique and with the behavior of other ionic glasses.

DC conductivity of silver vanadium tellurite glasses

The mixed electronic–ionic conduction in 0.5[ xAg 2O–(1− x)V 2O 5]–0.5TeO 2 glasses with x=0.1–0.8 has been investigated over a wide temperature range (70–425 K). The mechanism of dc conductivity changes from predominantly electronic to ionic within the 30⩽mol% Ag 2O⩽40 range; it is correlated with the underlying change in glass structure. The temperature dependence of electronic conductivity has been analyzed quantitatively to determine the applicability of various models of conduction in amorphous semiconducting glasses. At high temperature, T> θ D/2 (where θ D is the Debye temperature) the electronic dc conductivity is due to non-adiabatic small polaron hopping of electrons for 0.1⩽ x⩽0.5. The density of states at Fermi level is estimated to be N( E F)≈10 19–10 20 eV −1 cm −3. The carrier density is of the order of 10 19 cm −3, with mobility ≈2.3×10 −7–8.6×10 −9 cm 2 V −1 s −1 at 300 K. The electronic dc conductivity within the whole range of temperature is best described in terms of Triberis–Friedman percolation model. For 0.6⩽ x⩽0.8, the predominantly ionic dc conductivity is described well by the Anderson–Stuart model.

Correlation Between I-Ag Distance and Ionic Conductivity in AgI Fast-Ion-Conducting Glasses

A large number of AgI-based fast-ion-conducting glasses have been investigated by K-iodine extended x-ray absorption fine structure spectroscopy (EXAFS) measurements at liquid nitrogen temperature. A general correlation between the I-Ag distance measured by EXAFS and the glass activation energy for dc ionic conductivity has been found out: glasses with longer I-Ag distances display higher ionic conductivity, independently from the chemical composition of their host glassy matrix. This behavior can be related to the progressive increase of the "pathway volume" for ionic conduction.

Enhancement of DC ionic conductivity in dispersed solid electrolyte system—CsNO 3:γ-Al 2O 3

This paper reports the effect of heterogeneously doped alumina (γ-Al 2O 3) on the ionic conductivity of cesium nitrate (CsNO 3). Enhancement of conductivity is noticed to increase with mole percent (m/o) of the dispersoid. The maximum enhancement observed is about three orders of magnitude with respect to the host material. The experimental data indicating higher conductivity in dispersed system is interpreted in terms of the formation of space charge layer between the host material and dispersoid. The DSC results indicate that the addition of alumina to CsNO 3 leads to new phase boundaries at about 260 °C for the dispersed systems.

M/Li +( M = Mg 2+, Zn 2+, and Mn 2+) ion-exchange on lithium ion-conducting perovskite-type oxides and their properties

Lithium ions of perovskite-type lithium ion conductor La 0.55Li 0.35TiO 3 were replaced by divalent Mg 2+, Zn 2+, and Mn 2+ ions in an ion-exchange reaction using molten chlorides. The polycrystalline Mg-exchanged and Zn-exchanged samples are solid electrolytes for divalent Mg 2+ and Zn 2+ ions, whose dc ionic conductivities ( σ = 2.0 × 10 − 6 S cm − 1 at 558 K for the Mg-exchanged sample, La 0.56(2)Li 0.02(1)Mg 0.16(1)TiO 3.01(2) and σ = 1.7 × 10 − 6 S cm − 1 at 708 K for the Zn-exchanged samples, La 0.55(1)Li 0.0037(2)Zn 0.15(1)TiO 2.98(2)) were compared to those of the known highest Mg 2+ and Zn 2+ inorganic solid electrolytes. The Mn-exchanged sample, then, showed paramagnetic behavior in the temperature range of 2 to 300 K. The Mn ions in the exchanged sample are divalent and the spin configuration is in high spin state ( S = 5/2).

Relation between High Ionic Conductivity and Low-energy Dynamics in Superionic Conducting Glass

The mechanism of high ionic conductivity in superionic conducting glass still constitutes an unsolved problem in the field of science. We performed the inelastic neutron scattering measurements of superionic glass system (AgI)x(Ag2S)x(AgPO3)1-2x using the chopper spectrometer at high flux neutron spallation source. The dynamical properties over the wide range momentum-energy space were precisely compared between superionic glass and insulator glass. We found that the superionic glass shows larger intensity in low-energy region compared with undoped insulator glass, and the increase of low-energy intensity is undoubtedly correlated with the dc ionic conductivity. We also found the peculiar Q dynamics of low-energy excitation in superionic glass indicating the in-phase dynamical correlations. These characteristic features in low-energy dynamics must provide the new insight on the mechanism of superionic glass.

AC impedance analysis of CsNO3:Al2O3 composite solid electrolyte systems

Complex impedance spectroscopic studies were carried out on CsNO3 and CsNO3–Al2O3 dispersed solid electrolyte systems (DSES) in the temperature range of 100–350°C and the frequency 50kHz–1MHz. Dielectric constant, loss tangent, ac conductivity and dc ionic conductivity (obtained from CIS) in these systems are presented. DC ionic conductivity is noticed to increase with temperature in the extrinsic region in pure and dispersed systems. The enhancement of conductivity in DSES was observed to be about two orders of magnitude over its pure form in the extrinsic region. This enhancement of conductivity was attributed to the formation of space charge layer between the host material and the dispersoid. Enhancement in conductivity is found to increase with m/o up to 40m/o where as it decreased for 80m/o. Dielectric constant, dielectric loss and ac conductivity are also found to increase with temperature, and with mole percent it maintained the similar behavior as that of dc conductivity. These dielectric properties are interpreted in terms of space charge polarization and increased concentration of defects in the interfacial layer formed between the host and the dispersoid.

Conductivity Studies of Poly(ethylene oxide)/Copper Sulfate Solid Solutions

ABSTRACT ac and dc electrical conductivities of solid solutions of poly(ethylene oxide) (PEO) and copper sulfate (CuSO4) had been obtained from dielectric measurements as a function of temperature, frequency of applied electric field, and content of salt between 2% and 12% of CuSO4 by weight of PEO. The behavior of the dielectric constant with temperature showed evidence that the observed dielectric response was due mainly to migration of ions. The dielectric response was analyzed in the frame of the complex electrical modulus, from which it was possible to estimate values of dc ionic conductivity from 3,81 × 10−7 S/m for a content of 2% of salt to 5,5 × 10−6 S/m for a content of salt of 12% at room temperature, indicating an increase of the electrical conductivity by increasing the content of CuSO4. The behavior of ionic conductivity with temperature was compatible with the free volume model through the Volmer, Tamman, and Fulcher empirical equation. These preliminary experimental results allowed the conclusion that an electrolyte polymer has been prepared with base in poly(ethylene oxide)/copper sulfate mixtures, with a higher ionic conductivity in the order of 5,5 × 10−6 S/m at room temperature.