Impedance studies on plasticized PMMA-LiX [X: CF3SO3, N(CF3SO2)2−] polymer electrolytes

Plasticized polymer electrolytes composed of poly(methylmethacrylate) (PMMA) as the host, propylene carbonate (PC) or ethylene carbonate (EC) as a plasticizer and LiX (X: CF₃SO₃⁻ or N(CF₃SO₂)₂⁻) as a salt were prepared by the solution cast technique. Impedance spectroscopy was performed in the temperature range between 303 and 383 K. In this paper, we report the electrical properties of polymer electrolytes with different lithium salts and plasticizers. The polymer electrolytes investigated exhibited high ionic conductivity at room temperature in the range of 10^− 6 to 10^− 4 S cm^− 1. The temperature dependence studies showed that the samples were ionic conductors and seemed to obey the Vogel-Tamman-Fulcher (VTF) rule. FTIR spectroscopy studies confirmed the polymer-salt interaction.     

Investigation of fast-ionic transport in the ternary system (Cu1−xAgxI)-(Ag2O)-(V2O5), (0.05≤x≤0.25)

The occurrence of fast-ionic conduction in the ternary system 40(Cu_1−xAg_xI)-40(Ag₂O)-20(V₂O₅), (0.05≤x≤0.25) has been described. The formation of composite solid electrolyte materials comprising glassy and crystalline phases has been identified by means of X-ray diffraction analysis. Fourier transform infrared spectroscopic studies have confirmed the presence of VO₄³⁻ and V₂O₇⁴⁻ groups in these new materials. Detailed thermal characterization of these materials carried out by differential scanning calorimetry has indicated the transition temperature of one of the reaction products viz., AgI. From the conductivity measurements carried out using the complex impedance analysis, the values of room temperature electrical conductivity (σ_RT) and activation energy for ionic migration in these materials are found to be of the order of 10⁻² to 10⁻⁴ S cm⁻¹ and 0.22-0.35 eV, respectively. The ionic transport number (t_i) measurements made using Wagner’s polarization method and evaluation of silver ionic transport number (t_Ag⁺) by galvanic cell method have been used to estimate the extent of contribution of ionic conductivity especially due to silver ionic transport to the total conductivity observed in these materials.     

Ionic conductivity of a gel polymer electrolyte based on Mg(ClO4)2 and polyacrylonitrile (PAN)

Magnesium ion containing gel polymer electrolytes based on polyacrylonitrile (PAN) have been synthesized and characterized using ac impedance measurements. The electrolyte composition having the highest room temperature conductivity was found by varying the ratios propylene carbonate/ethylene carbonate (PC/EC) and PAN/Mg(ClO₄)₂. The corresponding composition was 18 mol% PAN:64 mol% EC:14 mol% PC:4 mol% Mg(ClO₄)₂. The ac conductivity measurements were carried out from room temperature upto 70 °C with blocking (stainless steel) electrodes. The room temperature conductivity is 3.2×10⁻³ S cm⁻¹ and the activation energy is 0.24 eV over the temperature range used. The high conductivity and the low activation energy of the material could possibly be due to the liquid electrolyte, Mg(ClO₄)₂ in EC/PC trapped in a matrix of PAN, as suggested by previous workers. According to dc polarization measurements, the gel electrolyte appears to be predominantly an anionic conductor.     

Novel composite interconnecting ceramics La0.7Ca0.3CrO3−δ/Ce0.8Sm0.2O1.9 for solid oxide fuel cells

In this paper, an interconnecting ceramic for solid oxide fuel cells was developed, based on the modification from La_0.7Ca_0.3CrO_3−δ by addition of Ce_0.8Sm_0.2O_1.9. It is found that addition of small amount Ce_0.8Sm_0.2O_1.9 into La_0.7Ca_0.3CrO_3−δ dramatically increased the electrical conductivity. For the best system, La_0.7Ca_0.3CrO_3−δ + 5 wt.% Ce_0.8Sm_0.2O_1.9, the electrical conductivity reached 687.8 S cm⁻¹ at 800 °C in air. In H₂ at 800 °C, the specimen with 3 wt.% Ce_0.8Sm_0.2O_1.9 had the maximal electrical conductivity of 7.1 S cm⁻¹. With the increase of Ce_0.8Sm_0.2O_1.9 content the relative density increased, reaching 98.7% when the Ce_0.8Sm_0.2O_1.9 content was 10 wt.%. The average coefficient of thermal expansion at 30-1000 °C in air increased with Ce_0.8Sm_0.2O_1.9 content, ranging from 11.12 × 10⁻⁶ to 12.46 × 10⁻⁶ K⁻¹. The oxygen permeation measurement illustrated a negligible oxygen ionic conduction, indicating it is still an electronically conducting ceramic. Therefore, this material system will be a very promising interconnect for solid oxide fuel cells.     

A novel gel polymer electrolyte based on polyacrylonitrile (PAN) and its application in a solar cell

A PAN-based gel polymer electrolyte with possible iodide ion conductivity was prepared by incorporating a mixture of Pr₄N⁺I⁻, iodine, EC and PC in PAN. Out of various compositions prepared and characterised, the sample with composition PAN (13%):EC (31%):PC (45%):Pr₄N⁺I⁻ (7%):I₂ (4%) by weight ratio, exhibited the maximum room temperature (25°C) conductivity of 2.95×10⁻³ S cm⁻¹. The predominantly ionic nature of the electrolyte was established by using the dc polarisation technique. The temperature dependence of ionic conductivity follows the VTF behaviour, indicating the amorphous nature of the electrolyte. Dye-sensitised photoelectrochemical solar cells prepared using this electrolyte exhibited an open circuit voltage (V_oc) of 0.69 V, a short circuit current (I_sc) of 3.73 mA cm⁻² for an incident light intensity of 600 W m⁻² yielding an overall quantum efficiency of 2.99%.     

Synthesis and characterisation of the garnet-related Li ion conductor, Li5Nd3Sb2O12

In this paper the synthesis, conductivity, and structure of the garnet-related Li ion conductor, Li₅Nd₃Sb₂O₁₂, are reported. As for the related Li₅La₃M₂O₁₂ (M = Nb, Ta) materials, this phase shows high Li ion conductivity, with a conductivity at 300 °C of 9.2 × 10⁻³ S cm⁻¹. Structural studies using neutron diffraction indicate a cubic unit cell, space group Ia-3d, with Li located in two partially occupied sites. One of the sites is the traditional garnet structure tetrahedral site, while the other Li site is considerably more distorted. Although the latter is nominally a six coordinate site, a close inspection suggests that the coordination could be described as distorted tetrahedral, with the remaining two bonds being significantly longer (≈2.6 Å).     

New cathode compositions based on La0.84Sr0.16Mn1−xMxO3, where M = Al, Ga for solid oxide fuel cell

In order to identify new cathode compositions for the high temperature solid oxide fuel cell, we have investigated the effect of the trivalent cations Al and Ga at the Mn site of the well-studied cathode composition La_0.84Sr_0.16MnO₃. All the compositions have been prepared by the low temperature citrate-nitrate auto-ignition process and sintered within the temperature range of 1150-1350 °C for 4 h. In order to understand the compatibility of the prepared samples as alternative cathode materials, we compared their electrical conductivity and thermal expansion coefficient with those of La_0.84Sr_0.16MnO₃ and yttria-stabilized zirconia. A 10 mol% Al doped La_0.84Sr_0.16MnO₃ composition exhibited a conductivity of around 122 S cm⁻¹ at 950 °C and a thermal expansion coefficient of 11.04 × 10⁻⁶ K with a minimum reactivity towards yttria-stabilized zirconia. Though the conductivity of the new composition is lower than that of La_0.84Sr_0.16MnO₃ (169 S cm⁻¹ at 950 °C), it is still high enough for use as a cathode material.     

Synthesis and conductivity of solid high-proton conductor H5GeW10MoVO40·21H2O

A new solid high-proton conductor decatungstomolybdovanadogermanic heteropoly acid (HPA) H₅GeW₁₀MoVO₄₀·21H₂O has been synthesized for the first time by stepwise acidification and stepwise addition of solutions of the component elements. The product was characterized by chemical analysis, potentiometric titration, IR, UV, XRD and TG-DTA. The IR, UV and XRD indicate that H₅GeW₁₀MoVO₄₀·21H₂O possesses the Keggin structure. The TG-DTA curve shows the sequence of water loss in the acid, the amount of the loss, as well as the thermostability. The results of AC impedance measurement show that its proton conductivity is 3.58 × 10⁻⁴ S cm⁻¹ at 18 °C and the activation energy for proton conduction is 31.82 kJ/mol.     

Lithium conducting glass ceramic with Nasicon structure

Lithium ion conducting glass and glass ceramic of the composition Li_1.4[Al_0.4Ge_1.6(PO₄)₃], have been synthesized. The monolithic glass pieces on thermal treatment resulted in single-phase glass ceramic with the Nasicon structure. Experiments with different electrodes proved that the lithium electrodes provide accurate values for the ionic conductivity using impedance spectroscopy. σ_ionic of the glass ceramic was found to be 3.8×10⁻⁵ S cm⁻¹ at 40°C with an activation energy (E_a) of 0.52 eV. The corresponding values for the glass are 2.7×10⁻⁹ S cm⁻¹ and 0.95 eV, respectively. The Arrhenius dependence of σ_ionic with temperature in glass and glass ceramic is interpreted with a hopping mechanism from which the microscopic characteristics of the lithium cation motion are deduced.     

Novel PEO-based composite solid polymer electrolytes incorporated with active inorganic–organic hybrid polyphosphazene microspheres

Inorganic–organic hybrid poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) microspheres with active hydroxyl groups were incorporated in poly(ethylene oxide) (PEO), using LiClO₄ as a dopant salt, to form a novel composite polymer electrolyte (CPE). The polymer chain flexibility and crystallinity properties are studied by DSC. The effects of active PZS microspheres on the electrochemical properties of the PEO-based electrolytes, such as ionic conductivity, lithium ion transference number, and electrochemical stability window are studied by electrochemical impedance spectroscopy and steady-state current method. Maximum ionic conductivity values of 3.36 × 10⁻⁵ S cm⁻¹ at ambient temperature and 1.35 × 10⁻³ S cm⁻¹ at 80 °C with 10 wt.% content of active PZS microspheres were obtained and the lithium ion transference number was 0.34. The experiment results showed that the inorganic–organic hybrid polyphosphazene microspheres with active hydroxyl groups can enhance the ionic conductivity and increase the lithium ion transference number of PEO-based electrolytes more effectively comparing with traditional ceramic fillers such as SiO₂.     

Transport characteristics of ZrO2 dispersed mixed (BaCl2)1−x-(KCl)x solid electrolytes

Composite solid electrolytes in the system [(BaCl₂)_1−x:(KCl)_x]_1−y:(ZrO₂)_y were prepared following the conventional ceramic powder processing route. In the mixed matrix system prepared by melt quench technique, a nominal increase in conductivity (σ) was found in (BaCl₂)_0.9:(KCl)_0.1. On ZrO₂ particle dispersion in this mixed matrix, the maximum conductivity (∼90 times that of base matrix value) was found to occur with 50 m/o of ZrO₂. Conductivity increases monotonically over the temperature range from 100 to 300 °C studied and attains the value of 10 × 10⁻⁶ S cm⁻¹ at 300 °C. The mobility (μ) of the charge carriers at room temperature was found to be 18.5 × 10⁻² cm² V⁻¹ s⁻¹ and the increase in μ with temperature was not very significant. The transference ionic number determination showed that the electrical conductivity of the electrolyte is predominantly due to ions. This study indicates that the conductivity is governed by mobile ion concentration.     

Electrical conductivity of yttrium-doped SrTiO3: influence of transition metal additives

The electrical conductivity of yttrium-doped SrTiO₃ with transition metals added as acceptor dopants (V, Mn, Fe, Co, Ni, Cu, Zn, Mo, Mg, Zr, Al, or Ga) was measured by the dc four-probe method at 600-900°C in reducing atmospheres. The replacement of 5 mol% titanium by acceptors leads to a decrease of conductivity of Sr_1−1.5xY_xTiO_3−δ. The degree of the decrease depends strongly on the type of dopant. Of the 5 mol% acceptor-doped compositions, the system Sr_0.85Y_0.10Ti_0.95Co_0.05O_3−δ had the highest conductivity of 45 S/cm at 800°C and oxygen partial pressure of 10⁻¹⁹ atm. The oxidation kinetics of yttrium-doped SrTiO₃ was significantly retarded by the addition of cobalt or manganese dopants. The ionic conductivity of SrTiO₃ doped with 5 mol% acceptors at Ti-sites was estimated from the total conductivity to lie in the vicinity of 10⁻⁴ S/cm, depending on oxygen partial pressure and temperature.     

Crystal structure and ionic conductivity of ruthenium diphosphate ARu2(P2O7)2, A=Li, Na, and Ag, with a tunnel structure

Crystal structure and ionic conductivity of ruthenium diphosphates, ARu₂(P₂O₇)₂ A=Li, Na, and Ag, were investigated. The structure of the Ag compound was determined by single crystal X-ray diffraction techniques. It crystallized in the triclinic space group P−1 with a=4.759(2) Å, b=6.843(2) Å, c=8.063(1) Å, α=90.44(2)°, β=92.80(2)°, γ=104.88(2)°, V=253.4(1) Å³. The host structure of it was composed of RuO₆ and P₂O₇ groups and formed tunnels running along the a-axis, in which Ag⁺ ions were situated. The ionic conductivities have been measured on pellets of the polycrystalline powders. The Li and Ag compounds showed the conductivities of 1.0×10⁻⁴ and 3.5×10⁻⁵ S cm⁻¹ at 150 °C, respectively. Magnetic susceptibility measurement of the Ag compound showed that it did not obey the Curie-Weiss law and the effective magnetic moment decreased as temperature decreased due to the large spin-orbital coupling effect of Ru⁴⁺ ions.     

Inkjet printing of conductive patterns with an aqueous solution of [AgO2C(CH2OCH2)3H] without any additional stabilizing ligands

The use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate, [AgO₂C(CH₂OCH₂)₃H], and its application as an aqueous metal-organic decomposition (MOD) inkjet ink is reported. The chemical and physical properties of the silver carboxylate and the ink formulated thereof are discussed. The ink meets all requirements of piezo driven inkjet printing. The printed features were converted into electrically conducting silver patterns by thermal or photo-thermal treatment. The conversion of [AgO₂C(CH₂OCH₂)₃H] to elemental silver follows a two-step decomposition as demonstrated by thermogravimetry-mass spectrometry (TG-MS) measurements. The measured conductivities of the printed features on glass and polyethylene-terephthalate (PET) are 2.7 × 10⁷ S m⁻¹ and 1.1 × 10⁷ S m⁻¹, respectively, which correspond to 43% (glass) and 18% (PET) of the bulk silver conductivity.     

Protonic conduction in Ca-doped La2M2O7 (M = Ce, Zr) with its application to ammonia synthesis electrochemically

Complex oxides La_1.95Ca_0.05M₂O_7−δ (M = Ce, Zr) were prepared by sol-gel method and characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD). On the sintered complex oxides as solid electrolyte, the conductivity was measured in various atmospheres, and ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in the solid states proton conducting cell reactor by electrochemical methods. The rates of ammonia formation were up to 2.0 × 10⁻⁹ mol s⁻¹ cm⁻² for La_1.95Ca_0.05Zr₂O_7−δ and 1.3 × 10⁻⁹ mol s⁻¹ cm⁻² for La_1.95Ca_0.05Ce₂O_7−δ, respectively, at 520 °C.     

Glass formation tendency in the system SeO2-Ag2O-B2O3

The glass formation regions in the system SeO₂-Ag₂O-B₂O₃ have been determined using the melt quenching method of evacuated silica ampoules. The structural units forming the amorphous network have been established by IR spectroscopy. The presence of SeO₃ (ν = 820 cm⁻¹; 760-750 cm⁻¹), BO₃ (ν = 1340, 1270 cm⁻¹) and BO₄ (ν = 1050 cm⁻¹) units has been confirmed. Crystallization of Ag₂SeO₃ only has been observed in a wide concentrate region near the glass formation boundary. A model explaining the unsatisfactory glass formation ability in the system investigated has been developed. It has been suggested that Ag⁺ ions are predominantly located near the selenite units, which stimulates the formation of isolated SeO₃ groups. The transformation of BO₃ into BO₄ units is hindered by the absence of free Ag⁺ ions near the borate units.     

Synthesis and spectroscopic investigations of Mn3O4 nanoparticles

Trimanganese tetraoxide (Mn₃O₄) nanoparticles have been synthesized via hydrothermal process. Nevertheless, homogeneous nanoparticles of Mn₃O₄ with platelet lozange shape were obtained. The crystallite size ranged from 40 to 70 nm. The Mn₃O₄ product was investigated by X-ray diffraction, transmission electron microscopy (MET), and impedance spectroscopy. Electrical conductivity measurements showed that the as-synthesized Mn₃O₄ nanomaterial has a conductivity value which goes from 1.8 10⁻⁷ Ω⁻¹ cm⁻¹ at 298 K, to 23 10⁻⁵ Ω⁻¹ cm⁻¹ at 493 K. The temperature dependence of the conductivity between 298 and 493 K obeys to Arrhenius law with an activation energy of 0.48 eV.     

SrSn1−xFexO3−δ (0≤x≤1) perovskites: a novel mixed oxide ion and electronic conductor

The electrical conductivity of SrSn_1−xFe_xO_3−δ increases with the Fe content and reaches a value of ∼10⁻¹ S/cm at 25°C at x=1. Compounds with low Fe content exhibit both ionic and electronic conductivity, while the higher Fe content perovskites are mainly electronic conductors with a conductivity independent of the oxygen partial pressure over a wide range from 0.21 to 10⁻²² atm.     

Study of Ln0.6Sr0.4Co0.8Mn0.2O3-δ (Ln=La, Gd, Sm or Nd) as the cathode materials for intermediate temperature SOFC

Perovskite type oxides Ln_0.6Sr_0.4Co_0.8Mn_0.2O_3−δ (Ln=La, Gd, Sm, or Nd) have been prepared by the solid state reaction of corresponding oxides. The crystal parameters of the compositions were determined by XRD powder diffraction, which revealed that all the compositions have orthorhombic structure. The reaction test of all samples with Ce_0.8Gd_0.2O_1.9 was carried out at 1200 °C for 48 h, and no reaction product was detected by XRD. The change in mass of La_0.6Sr_0.4Co_0.8Mn_0.2O_3−δ as a function of temperature was determined by thermogravimetric analysis (TGA). The electrical conductivity of the sintered samples were measured as a function of temperature from 200 to 1000 °C. The highest conductivity of about 1400 S cm⁻¹ was found in La_0.6Sr_0.4Co_0.8Mn_0.2O_3−δ. The cathodic polarization of these oxides electrodes deposited on Ce_0.8Gd_0.2O_1.9 tablet was studied at 500-800 °C in air.     

Gel polymer electrolytes based on polyacrylonitrile and a novel quaternary ammonium salt for dye-sensitized solar cells

Gel polymer electrolytes were prepared by incorporating polyacrylonitrile (PAN) in a mixture of polysiloxane with quaternary ammonium side groups (PSQAS), ethylene carbonate (EC), propylene carbonate (PC) and iodine. The influence of PAN content on the ionic conductivity of gel polymer electrolytes and the charge-transfer kinetic performance in counterelectrode-electrolyte interface was investigated. The dye-sensitized solar cell with the gel polymer electrolyte containing 5 wt.% PAN showed the best photovoltaic performance; a maximum incident photon conversion efficiency of 63% at 520 nm was obtained, the short-circuit photocurrent density (J_sc), the open-circuit voltage (V_oc) and the fill factor (FF) were 7 mA cm⁻², 0.565 V and 0.65, respectively. The corresponding overall conversion efficiency (η) is 4.3%.