Complex Impedance Method Research Articles

Chemically Driven Ion Exchanging Synthesis of Na5YSi4O12-Based Glass-Ceramic Proton Conductors

We have developed 12-membered silica-tetrahedra-ringed Na5YSi4O12-type sodium ion conducting glass-ceramics on the basis of the composition Na3+3x-yR1-xPySi3-yO9 (R: rare earth elements; denoted as Narpsio); especially, the material of Na4Y0.6P0.2Si2.8O9 with the combined parameters of (x, y) = (0.4, 0.2) gives rise to the maximum conductivity of 1 × 10-1 Scm-1 at 300 °C. Because glass-ceramics generally have the advantage of structural rigidity and chemical durability over sintered polycrystalline ceramics, the present study employed glass-ceramic Narpsio to perform chemically driven ion exchange of Na+ with protonated water molecules with an aim to produce a proton conductor. The ion exchange was carried out in a hydrochloric acid solution by changing immersion time, temperature, and acid concentration. The ion exchanged Na4Y0.6P0.2Si2.8O9-based glass-ceramics were analyzed by the complex impedance method, and the proton conductivity was found to exhibit 3 × 10-4 Scm-1 at 300 °C with the activation energy of 59 kJ/mol. The dependence of humidity-sensitive conductivity of the ion exchanged bulk glass-ceramics was also examined; the conductivity increased almost linearly from 0.6 × 10-4 Scm-1 in dry air to 1.5 × 10-4 Scm-1 in 75% humid ambience at 300 °C. Thus, the ion exchanged glass-ceramics can be considered to be high temperature proton conductors as well as humidity sensors.

Диэлектрическо-спектроскопическая сепарация характеристик механизмов проводимости в нанкристаллическх пленках AgI

The study of the frequency dependence of the components of the complex permittivity of thin (100 nm) nanocrystal silver iodide (AgI) films revealed the presence of two different types of relaxation processes, sharply differing in their relaxation times: tau1<<tau2. It is established that the small relaxation time of tau1 is the time of formation of a stable configuration of the internal electric field when the external high-frequency sinusoidal electric field is shielded by a system of free conduction electrons. On the contrary, a long relaxation time of tau2 characterizes the process of shielding a low-frequency external field by a system of quasi-free silver ions. It is shown that the temperature dependence of the numerical value of tau1(T) has a thermal hysteresis with a loop, the position of the heating and cooling branches of which coincides with the temperature region of the forward and reverse phase transitions in the AgI film: semiconductor-superionic and superionic-semi-conductor. The results of calculating the parameters of dielectric spectra in the framework of Debye theory are presented, demonstrating good agreement with the parameters of the proposed electrical circuit of the film sample calculated by the complex impedance method

Photoelectrochemical Hydrogen Production System Using Li-Conductive Ceramic Membrane.

Based on the LiLaTiO3 compound, a ceramic membrane for a photoelectrochemical cell was created. The microstructure, phase composition, and conductivity of a semiconductor photoelectrode and a ceramic membrane were studied by using various experimental methods of analysis. A ceramic Li conducting membrane that consisted of Li0.56La0.33TiO3 was investigated in solutions with different pH values. The fundamental possibility of creating a photoelectrochemical cell while using this membrane was shown. It was found that the lithium-conductive membrane effectively works in the photoelectrochemical system for hydrogen evolution and showed a good separating ability. When using a ceramic membrane, the pH in the cathode and anode chambers of the cell was stable during 3 months of testing. The complex impedance method was used to study the conductive ceramic membrane in a cell with separated cathode and anode chambers at different pH values of the electrolyte. The ceramic membrane shows promise for use in photoelectrochemical systems, provided that its resistivity is reduced (due to an increase in area and a decrease in thickness).

Study of ionic conduction, dielectric relaxation, optical and electrochemical properties of AgPO3/graphene glasses for magnesium battery applications

Developing suitable cathode material for alkali ion batteries is the most significant challenge facing commercialization. The effect of graphene nanoplatelets (GNP) on the physical and optical properties of AgPO3 glass is demonstrated. For the first time, AgPO3/Graphene glasses have been synthesized by melt-quenching method to assess the physical and the electrochemical performance as a cathode for a Magnesium ion battery. The complex impedance method determines bulk conductivity; the bulk conductivity increases with increasing temperature and graphene content. AgPO3_2 wt%GNP (sample 2) shows the optimum stoichiometric ratio with linear conductivity-temperature growth up to fast-ionic conductivity ∼ 1.79×10−2 (ohm. cm)−1 at 150 °C. The study of frequency dependence of both dielectric constant and dielectric loss have been explained based on ion hopping beside the ionic polarization mechanism. Optical properties such as the refractive index, optical energy gap, molar refractivity, molecular polarizability, dispersion, and oscillator energy of AgPO3 glass with different graphene nanoplatelets are investigated. The data reveal the lowest energy gap for the glass sample (AgPO3/2 wt%GNP). On the contrary, the values of refractive index, dispersion energy, molar refractivity and molecular polarizability are the highest for (AgPO3_2%wt%GNP) sample. The coin cell has been fabricated with the cell configuration Mg//electrolyte//AgPO3 and Mg//electrolyte//AgPO3_2 w%GNP. The cell with AgPO3_2 wt% GNP electrode has a high initial discharge capacity of ∼187 mAh/g compared with AgPO3 electrodes of ∼100 mAh/g.

Electrical polarization and ionic conduction properties of β-tricalcium phosphate bioceramics with controlled vacancies by sodium ion substitution

With the aim to understand electric polarization mechanisms of β-tricalcium phosphate as an advanced biomaterial, Na ion-substituted β-Ca3(PO4)2 (Na-β-TCPs) ceramics with controlled lattice vacancies were synthesized and structural refinement was performed by the Rietveld method. The Rietveld analysis revealed that Ca and vacancies at Ca(4) sites in the β-TCP structure decreased with an increase in Na substitution. Electrical measurements by the complex impedance method revealed that the conductivity and the activation energy calculated from Cole-Cole plots rapidly decreased to a constant value with an increase in Na substitution and decrease in vacancies. The thermally stimulated depolarization current (TSDC) curve of the electrically polarized Na-β-TCP showed one large peak at 530–610 °C. However, the accumulated charge decreased with an increase in Na ions and decrease in vacancies up to 2.37 mol%, after which it became constant. These results are consistent with the presumed formation of a dipole moment between aligned Ca2+ ions and their vacancies along the direction of the external polarization field applied at high temperature. We conclude that the large amount of stored charge in β-TCP caused by electrical polarization is due to the low site occupancy of calcium ions and vacancies at Ca(4) sites in the β-TCP structure, which is not the case for hydroxyapatite (HAp), as previously reported.

Structure and lithium-ion conductivity investigation of the Li7-xLa3Zr2-xTaxO12 solid electrolytes

Currently solid electrolytes with high values of lithium-ion conductivity are required for creation high-energy lithium and lithium-ion power sources, including all-solid-state batteries. Compounds with a garnet structure based on Li7La3Zr2O12 are promising solid electrolytes for such power sources. In presented work solid electrolytes in the Li7-xLa3Zr2-xTaxO12 system were synthesised using the sol-gel method in a wide concentration range of tantalum from x=0 to x=2.0. According to X-ray diffraction analysis, compounds with x > 0 has a cubic modification with the space group Ia-3d. The electrical resistance of the obtained solid electrolytes was measured by the complex impedance method in the temperature range of 25-210 °C, and the values of total lithium-ion conductivity were calculated. It was found that Li6.4La3Zr1.4Ta0.6O12 has the maximum values of lithium-ion conductivity in studied system – 1.4•10−4 S/cm at 25 °C. The Density Functional Theory modeling confirms that moderate Ta-doping is most suitable for enhancing of Li diffusion.

Effect of vanadium doping on the electrical charge transport and dielectric relaxation properties of Sodium Bismuth Titanate perovskite

In this work, we report the effect of vanadium doping on the conductivity and relaxation dynamics of the charge carriers in Sodium Bismuth Titanate perovskite material (Na0.5Bi0.5TiO3) prepared by a unique technique which is a combination of chemical and mechanical methods. The parent material was prepared using the citrate auto-ignition method and the mechanical alloying technique was used to incorporate V2O5 in the NBT structure. The X-ray diffraction analysis confirmed the formation of the rhombohedral phase of NBT perovskite with space group R3c in all the compositions. The microstructural analysis was done using Field Emission Scanning Electron Microscopy, Energy-dispersive X-ray spectra, and the elemental mapping of the samples. The conductivity mechanism was analyzed using the complex impedance method. The sample with 15% doping showed the highest conductivity with minimum activation energy. The activation energies for conduction, relaxation, and migration of charge carriers were found to be comparable with each other. The frequency-dependent dielectric data was analyzed using Havriliak–Negami (HN) formalism and suggested non-Debye type relaxation behaviour. The 15% dopped composition showed the highest dielectric strength. The scaling behaviour of impedance and modulus spectra confirmed the temperature-independent conduction and relaxation mechanisms.

Electrical Impedance and Modulus Characteristics of Bulk PZT Ceramics Modified by Mn and Ce

The compounds of Pb(Zr0.35-xYxTi0.65)O3 (x = 0.00, 0.10 and Y = Mn/Ce) stoichiometry were prepared by a standard solid state route of mixing. The lead zirconatetitanate (PZT) has been modified by substituting 10% of manganese (Mn+4), and cerium (Ce+4) ions, by replacing zirconium (Zr+4). The effect of substitution of Mn+4 and Ce+4 ions, on the electrical properties of PZT based ceramics, has been investigated systematically in this work. To study the impedance and modulus characteristics, adopted are the complex impedance and complex modulus spectroscopic methods respectively. Results indicated that the compounds exhibit negative coefficient of resistance behavior (as evident from impedance spectra), and real ionic conductor nature (as evident from modulus spectra). The electrical properties of the compounds are primarily dominated by the grains rather than grain boundaries and electrode-material interface polarization.

Synthesis and characterization of Na+ conducting glass-ceramic Na5FeSi4O12 doped with boron, aluminum, and gallium oxides

Sodium-ion conductive glass-ceramics of Na5FeSi4O12 were successfully synthesized through the crystallization of glasses with the composition Na5FeSi4O12. The optimum crystallization conditions and the kinetics of the glasses were examined by differential thermal analysis. The characterization of crystallization and conduction properties were performed on thus obtained glass-ceramic Na5FeSi4O12 by a non-isothermal modified Kissinger and complex impedance methods, respectively. The activation energy for crystallization was 279 kJ mol−1 and the sodium-ion conductivity was obtained as 1.33 × 10−3 S cm−1 at 300 °C. To improve the conductivity with a small amount of Si-substitutes, Na5FeSi4O12-isostructural derivatives containing such as B, Al, and Ga were also prepared according to the same crystallization process of glasses with the composition Na5.1FeM0.1Si3.9O12 (M = B, Al, Ga). Without phase separation, the ionic conductivities of glass-ceramics were enhanced up to 1.69 × 10−3 at 300 °C on Na5.1FeB0.1Si3.9O12, whereas decreased down to 1.30 × 10−3 and 1.12 × 10−3 S cm−1 at 300 °C on Na5.1FeAl0.1Si3.9O12, and Na5.1FeGa0.1Si3.9O12, respectively.

Investigation of resistive, capacitive and conductive properties of lead-free electronic material: 0.7Bi(Fe0.98Ga0.02)O3-0.30BaTiO3

The polycrystalline 0.7Bi(Fe0.98Ga0.02)O3-0.30BaTiO3 (BFG-BTO) ceramic was processed by high temperature reaction route. The room temperature X-ray spectra suggest a tetragonal symmetry. The structural refinement was also carried out. The high densification of sample formation is depicted from a scanning of the natural surface of the sample. The electrical properties were measured using a complex impedance method over a wide range of frequencies and temperatures. The overlapping large-polaron tunnelling model type of conduction mechanism is obtained from the frequency dependent ac conductivity plots. The relaxation mechanism is studied with the help of various spectroscopic tools (modulus and dielectric). The Nyquist plot indicates the non-Debye characteristics and the combined contribution of both grain and grain boundary towards the resistive property of the sample.

A Novel Voltage Stabilization and Power Sharing Control Method Based on Virtual Complex Impedance for an Off-Grid Microgrid

Microgrid (MG) usually operates in medium/low-voltage systems, where the line impedance parameters are mainly resistive, and traditional P-f/Q-U droop control is no longer applicable. When the virtual complex impedance method is adopted, the resistance component of line impedance can be counteracted by a virtual negative resistance. Unfortunately, the improper design of the virtual negative resistance will result in an unstable system due to the problem of line impedance parameter drift and estimation error. According to the line parameters characteristics of the off-grid MG with medium/low voltage, the P-U/Q-f droop control is adopted in this study, where the virtual complex impedance composed of a virtual negative inductance and a virtual resistance is introduced in the control loop. The virtual negative inductance is used to reduce the power coupling caused by the inductive component of the system impedance. The virtual resistance is implemented to enhance the resistive component and adjust the impedance matching degree for raising the accuracy of power sharing. However, the power sharing is still affected by the system hardware parameters; meanwhile, the voltage deviation caused by the droop control and the virtual impedance exists. In this study, a novel voltage stabilization and power sharing control method based on the virtual complex impedance is investigated to achieve accurate power sharing without the impact of hardware parameters variations and to improve the voltage quality. Moreover, the small-signal model of the inverter-based off-grid MG with the proposed controller is established, which can be utilized to analyze the stability and dynamic performance of the system. Meanwhile, the control parameters can be sequentially determined. Analysis shows that the strategy is robust against the line-impedance parameter drift and the estimation error and has a large stability margin and fast dynamic-response speed. Finally, numerical simulations and experimental results are provided to verify the effectiveness of the proposed control method in comparison with traditional frameworks.

Characterization of scrutinyite SnO2 and investigation of the transformation with 119Sn NMR and complex impedance method

Scrutinyite SnO2 was synthesized by annealing SnO nanoparticles fabricated from micron-size SnO via ball milling. The isotropic as well as anisotropic chemical shifts of 119Sn obtained by solid-state nuclear magnetic resonance method, were verified computationally using a pseudopotential method in density-functional theory. The results fit with 6-fold coordinated Sn. A linear relationship holds empirically between isotropic shift and coordination number divided by Sn-O average bond length in all polymorphs of tin oxides. When the annealing proceeded in an oxygen-free atmosphere, metallic tin, the rutile phase of SnO2 and oxygen vacancies associated with permanent electric dipoles were also detected by thermal analysis and dielectric spectroscopy.

Structural, morphological and electrical properties of multi-doped calcium phosphate materials as solid electrolytes for intermediate temperature solid oxide fuel cells

Modified solution precipitation method was used to prepare pure and doped Mg, Sr and Na hydroxyapatite type materials (CaP, CaMgP and CaSrNaP). Modification consisted of partial substitution of nitrates by acetate solution in order to achieve a more soluble and cost effective synthesis. The obtained samples were calcined at 400?C (CaP400, CaMgP400 and CaSrNaP400). All powders were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Calcined samples were densified at 1000?C in an air for 3 h (CaP1000, CaMgP1000 and CaSrNaP1000). Sintered samples were characterized by XRPD, FTIR, SEM, EDS and complex impedance methods. The highest conductivity was found for the multi-doped phosphate sample (CaSrNaP1000) at 700?C (1.90?10-3?-1cm-1). The corresponding activation energies of conductivity amounted to 0.31 eV in the temperature range 500-700?C.

STRUCTURAL AND OPTOELECTRONIC PROPERTIES OF SnO2 THIN FILMS DOPED BY GROUP-IA ELEMENTS

This paper presents the results of an experimental work devoted to the synthesis and the characterization of tin dioxide (SnO[Formula: see text] thin layers doped with group-IA elements (Li, Na and K). The materials were synthesized by the sol–gel method and deposited by dip-coating, using tin (II) chloride dihydrate as a source of tin and absolute ethyl alcohol as solvent. Thin films prepared were characterized by several techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), visible and ultraviolet spectroscopy and complex impedance method. The results obtained show that the materials kept their tetragonal rutile structure with preferred orientation of (101), whereas doping leads to a reduction of their energy band gap. The complex impedance analysis suggests that the different processes occurring at the electrode interface are modeled by an electrical circuit not affected by the doping.

Properties and Lithium Battery Applications of Solvate Ionic Liquid/CO2 Binary Mixtures

Introduction We have previously reported the intriguing physico-chemical properties of a series of solvate ionic liquids (SILs), which share many of the features of conventional ionic liquids, including high thermal stabilities, wide electrochemical windows and high ionic conductivities, making them attractive as electrolytes for future energy storage applications.1,2SILs may be exemplified by the 1:1 combination of Li[TFSA] and tetraglyme (G4), forming [Li(G4)][TFSA], shown in Fig.1. Recently, we extended our study of the properties of these SILs upon dilution with several molecular solvents.3 An important criterion4 of a SIL is the stability of the complex cation i.e. [Li(G4)]+. This can be conveniently determined by pulsed field gradient NMR (ratio of self-diffusion coefficients Dglyme/DLi is approximately unity), and furthermore by assessment of the residual (“free”) glyme in solution by Raman spectroscopy (deconvolution of the relevant modes gives typically <5% “free” glyme). Of particular note are the low polarity solvents such as toluene and HFE (1,1,2,2-tetrafluoroethyl,2,2,3,3-tetrafluoropropyl ether), which can effectively dilute the SILs, decreasing viscosity and increasing ionic conductivity, without disruption of the complex cation, [Li(G4)]+. Indeed, we have previously demonstrated the use of HFE in particular as a diluting solvent for a SIL applied to the lithium-sulfur battery.5Dilution of the SIL with HFE enables increased coulombic efficiency and rate capability, and also further reduces the solubility of the polysulfides. Moreover, as HFE is a non-flammable diluting solvent, the inherent safety advantage of the low-volatility SIL is not compromised. However, the use of a perfluorinated diluting solvent may be problematic environmentally. The formation of binary mixtures of ILs and high pressure carbon dioxide (CO2) has been studied extensively.6 As a low polarity solvent, it is reasonable to assume that CO2 would also not disrupt the complex cation structure of the SIL. Inspired by these analogous systems, we report here our findings for the dilution of a SIL with environmentally benign, high pressure CO2. Experimental Conductivity was measured by the complex impedance method with two platinum electrodes. The cell constant was determined by calibration with a dilute KCl solution, before transfer of the electrode assembly to the high pressure vessel. The determination of solubility of CO2 in the SIL was performed as described in detail elsewhere.7 Briefly, (i) the pressure change upon sorption of a known quantity of CO2 in the SIL, and (ii) the volume expansion of the SIL upon CO2sorption were determined, from which the solubility could be calculated. The Li deposition/dissolution and battery measurements were performed in a hand-made screw-plate cell that was assembled and then placed inside the high pressure vessel in an Ar-filled glovebox. Results and Discussion The large solubility of CO2 in the SIL promotes a dramatic enhancement in conductivity, as shown in Fig.2 below. This increase is conductivity is not unprecedented. Notable earlier reports in this area include that of Tominaga et al., who, after studying the effect of high pressure CO2 processing on polymer electrolytes, observed in situ a significant enhancement in conductivity for a series of solid polymer electrolytes, such as PMEO10LiTFSA (PMEO: poly-(oligo-oxyethylene glycol methacrylate)), under CO2 pressure.8 The reversible deposition and dissolution of lithium metal was studied in this SIL/CO2 binary mixture, as shown in Fig.3. The result obtained under Ar pressure is also shown for comparison. CO2, with high solubility, promotes efficient deposition and dissolution of Li. This can in part be attributed to higher conductivity (the use of high pressure Ar does not dramatically change the conductivity of the SIL). As shown in Fig.4, the binary SIL/CO2 mixture can also be applied to a typical Li-ion battery cathode such as LiCoO2(LCO), showing improved energy efficiency. In our presentation of this work, we will further discuss the solution properties of the SIL/CO2binary system, further electrochemical characterisation of the Li deposition/dissolution process, and comment on the application of this novel electrolyte for other conventional battery electrodes, including graphite. Acknowledgement This study was supported in part by the Advanced Low Carbon Technology Research and Development Program (ALCA) of the Japan Science and Technology Agency (JST).

Influence of Crystal Growth Cooling Conditions on Thermoelectric Properties of Aurivillius Phase Bi-V-O

Aurivillius phase Bi2VO5.5 is known as an oxygen ion conductor. In previous studies on Bi2VO5.5, the Seebeck coefficient of the sintered body was about 10 mVK−1 at 800 K. However, the resistivity was 103 Ω m at 800 K. It seemed that this high resistivity was caused by high grain boundary resistance because of cracks at boundaries. In this study, specimens have been prepared by a melting method, aimed at reducing the boundaries. The influence of crystal growth cooling conditions on the thermoelectric properties of Aurivillius phase Bi-V-O is discussed. The crystal growth cooling conditions investigated were slow cooling with cooling rate of 9 K h−1, furnace cooling, and quenching. The surface and cross-section of the sample were observed by scanning electron microscopy (SEM). The crystalline phase was identified by x-ray diffraction (XRD) analysis. The resistivity was measured by the direct current (DC) two or four terminals method. The Seebeck coefficient was measured by the small temperature difference method. The transgranular resistance and grain boundary resistance were evaluated by the complex impedance method. All samples consisted of layered grains. The grain thickness at cross section decreased with increasing cooling rate. The resistivity of the quenched and slowly cooled specimens was approximately 1000 times lower compared with the furnace cooled specimen and sintered body over the measured temperature range.

Enhancement of Ionic Conductivity of Composite Membranes for All-Solid-State Lithium Secondary Batteries

Recently, significant attention has been paid to conventional lithium ion battery (LIBs) with large-scale energy storage and longer cycle properties because new applications, such as electric vehicles (EVs) and energy storage systems (ESSs), are gradually emerging onto the market. Moreover, large-scale battery systems are needed to reduce the system costs of these new applications. Safety issues are of even greater concern for such batteries than for existing smaller batteries. As a promising solution to these issues, the use of a solid electrolyte (SE, based on a polymer and a ceramic) has been suggested [1-2]. In contrast to organic-based liquid electrolytes, all-solid-state lithium ion batteries with a solid electrolyte are considered safe because of their non-flammability. Various solid electrolytes based on high molecular weight dielectric polymer hosts have been tested, and in particular dry electrolyte membranes based on polyethylene oxide (PEO) have been widely studied. PEO-based membranes can be used in all-solid battery designs in a free standing form without modifying current battery fabrication processes[3]. However, the ionic conductivities of PEO-based membranes are very low (10- 6-10- 8 S/cm) at the room temperature because of their low effective carrier mobilities. The carrier mobility can be enhanced by stabilizing the highly conductive amorphous matrix with an inorganic filler (nano-sized SiO2, Al2O3, etc.) [4-5]. However, high ionic conductivities (>10- 4S/cm) can only be obtained in these composites when they have very high filler contents (e.g. >30 wt.%), which result in poor process ability and mechanical properties [6]. In this study, we propose the new concept of a free-standing composite membrane with high ionic conductivity and good process ability, and report our implementation of this concept through the incorporation of garnet-type LLZO solid electrolyte powder into a PEO polymer matrix. Further, we discuss whether the ion conductivity of the composite membrane is improved by adding a small amount of Ionic liquids (ILs) with LLZO solid electrolyte powder because of synergetic effects, and whether the mechanical flexibility of the composite membrane is maintained. Finally, we assess the feasibility of all-solid electrode designs that use oxide solid electrolyte powders. Li7La3Zr2O12 powders were purchased from Nikkiso Co. Ltd. and used as received. The LiClO4/PEO molar ratio was fixed at 1:6, and the amount of LLZO was varied from 37.5 to 47.5 wt.% with respect to the total PEO+LLZO weight of the composite membrane. PEO, LiClO4, and LLZO were simply mixed in acetonitrile (ACN), and the ACN component of the slurry was slowly evaporated at room temperature in a dry-room, resulting in composite solid electrolyte membranes with various LLZO contents in a PEO matrix. Also, optimum condition of the composite membrane with a small amount of ILs was prepared. The ionic conductivity of the electrolytes was determined through complex impedance method using an AC impedance analyzer. The cathode electrode with the optimum composition was prepared as follows. LiNi0.6Co0.2Mn0.2O2/PEO/ LLZO/LiClO4/carbon black (60:15:17.5:2.5:5 wt%) were mixed to create the cathode slurry. A coin cell (2032 type) was fabricated in a dry-room using a composite cathode electrode, solid electrolyte membranes and Li foil anode. The charge-discharge measurements were carried out within 2.5-4.3V. Fig.1a shows the variations of the ionic conductivity of the composite membranes with LLZO content. Increasing the LLZO content from 37.5% to 47.5% enhances the ionic conductivity slightly, but further increases in the LLZO content result in decreases in the ionic conductivity. The composite membrane with the maximum ionic conductivity was prepared under optimum conditions with 42.5% LLZO and 52.5% PEO-LiX. Thus the incorporation of the inorganic phase (LLZO) into the organic matrix (PEO-LiClO4) has a synergetic effect on the Li ionic conductivity. The ionic conductivity of the as-synthesized composite membrane was found to be significantly enhanced with respect to those of PEO-only and LLZO-only membranes, and the optimum composition was determined. Fig.1b shows the variations of the ionic conductivity of the composite membranes with ILs amount. In our approach to enhancing ionic conductivity while retaining a free standing design, we combined the organic matrix (PEO-LiX) and an inorganic solid electrolyte (LLZO) with small amount of ILs to form a composite membrane. The ionic conductivity is increased with adding ILs because the composite membrane of ILs to assist in the formation of ionic contacts. References R. Kanno et al., J. Electrochem. Soc. 148 (2001) A742-A746. A. Hayashi et al., Electrochem. Commun. 5 (2003) 111-114. J. MacCallum, C. Vincent, Polymer Electrolytes Reviews I, Elsevier, London, 1987. B. Scrosati et al., J. Electrochem. Soc. 147 (2000) 1718-1721. L. Persi et al., J. Electrochem. Soc. 149 (2002) A212-A216. X.-W. Zhang et al., J. Power Sources 112 (2002) 209-215. Figure 1

Rietveld refinement, electronic structure and ionic conductivity of Sr4La6(SiO4)6F2 and Sr4La6(SiO4)6O ceramics

In this paper, we report the effect of the tunnel anions on the ionic conductivity of Strontium-Lanthanum silicate apatites. The Sr4La6(SiO4)6F2 and Sr4La6(SiO4)6O ceramics were prepared by the solid state reaction method. X-ray diffraction, NMR spectroscopy and Raman measurements were performed to investigate the crystal structure and vibrational active modes. Moreover, the electronic structures of the crystals were evaluated by the first-principles quantum mechanical calculation based on the density functional theory. Finally, the ionic conductivity was studied according to the complex impedance method.

Complex Impedance Analyses of Ba&lt;sub&gt;1-&lt;/sub&gt;&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;Li&lt;sub&gt;0.5&lt;/sub&gt;&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;Bi&lt;sub&gt;0.5&lt;/sub&gt;&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;TiO&lt;sub&gt;3&lt;/sub&gt; Solid Solution PTCR Ceramics

Conditions for the formation of (1-x)BaTiO3–xLi0.5Bi0.5TiO3 (0 ≤ x ≤0.6) solid solutions with positive temperature coefficient of resistance (PTCR) effect were studied. Solid solutions were prepared by solid state reaction technique. Samples were sintered under reducing atmosphere N2/H2 in the temperature range 1200–1450 °C with subsequent oxidation in air. The phase composition was investigated by X-ray powder diffraction method. It was found that samples of (1-x)BaTiO3–xLi0.5Bi0.5TiO3 (0 ≤ x ≤0.6) solid solutions at room temperature exhibit perovskite structure. Unit cell parameters of unstable at the room temperature compound Li0.5Bi0.5TiO3 were determined by extrapolation of concentration dependence of the unit cell parameters in the (1-x)BaTiO3–xLi0.5Bi0.5TiO3 system. It was shown that minimum value of resistivity ρmin rises with increase in x value. Complex impedance method shown that ceramic grains of (1-x)BaTiO3–xLi0.5Bi0.5TiO3 materials consist of three areas with different electrical properties. Boundary and outerlayer region of grains make the main contribution to the PTCR effect in lithium-containing solid solutions. It was shown that magnitude of the potential barrier's decreases with increasing x.

Structural, morphological, and electrical properties of doped ceria as a solid electrolyte for intermediate-temperature solid oxide fuel cells

The solid solutions of CeO2 with one or more rare-earth oxides among Yb2O3, Sm2O3, and Gd2O3 are synthesized by either modified glycine nitrate procedure (MGNP) or self-propagating reaction at room temperature (SPRT). The overall mole fraction of rare-earth oxide dopants was x = 0.2. The characterization was committed by XRPD, TEM, BET, and Raman Spectroscopy methods. According to XRPD and Raman spectroscopy, the obtained products presented the single-phase solid solutions with basic fluorite-type CeO2 structure, regardless on the number and the concentration of dopants. Both XRPD and TEM analysis evidenced the nanometer particle dimensions. The defect model was applied to calculate lattice parameters of single-, co-, and multi-doped solids. The sintering of the sample nanopowders was performed at 1550 °C, in air atmosphere. The sintered samples were characterized by XRPD, SEM, and complex impedance methods. The sintering did not affect the concentration ratios of the constituents. The highest conductivity at 700 °C amounting to 2.14 × 10−2 and 1.92 × 10−2 Ω−1 cm−1 was measured for the sample Ce0.8Sm0.08Gd0.12O2−δ, synthesized by SPRT and MGNP methods, respectively. The corresponding activation energies of conductivity, measured in the temperature range 500–700 °C, amounted to 0.24 and 0.23 eV.