Study of effect of composition, irradiation and quenching on ionic conductivity in (PEG) x : NH4NO3 solid polymer electrolyte

We have prepared, characterized and investigated a new PEG-2000 based solid polymer electrolyte (PEG) _x : NH₄NO₃. Ionic conductivity measurements have been made as a function of salt concentration as well as temperature in the range 265–330 K. Selected compositions of the electrolyte are exposed to a beam of 8 MeV electrons and ⁶⁰Co γ-rays to an accumulated dose of 10 kGy to study the effect on ionic conductivity. The electrolyte samples are also quenched at liquid nitrogen temperature and conductivity measurements are carried out. The ionic conductivity at room temperature exhibits a characteristic peak for the composition, x = 46. Electron beam irradiation results in an increase in conductivity for all compositions by a factor of 2–3. Exposure to γ-rays enhances the conductivity by one order of magnitude. Quenching at low temperature has resulted in an increase in conductivity by 1–2 orders of magnitude. The enhancement of conductivity upon irradiation and quenching is interpreted as due to an increase in amorphous region and decrease in crystallinity of the electrolyte. DSC and NMR measurements also support this conclusion.     

Conductivity and strength behaviour of aluminawhisker-zirconia composites

Yttria stabilized zirconia (8 mol%) composites were fabricated by tape casting with either alumina powder or alumina whiskers, and pressureless sintered. Sintering behaviour, ionic conductivity and mechanical strength were analysed. For all compositions analysed, increasing alumina content reduced the sintered density. For whisker-reinforced zirconia, the rigid whiskers prevented matrix densification along their axis. The ionic conductivity was measured by the complex impedance method from 500–1000 °C and the activation energy for ionic conduction calculated over that range. The ionic conductivity of the alumina-zirconia composites decreased with increasing alumina content as expected by the rule of mixtures. However, the ionic conductivity of the whisker-zirconia composites decreased more than expected possibly due to contamination from the whiskers. The strength of the whisker-zirconia composites was also found to be affected by the porosity. At 5 vol%, the average strength was measured at 39.9 kgf mm^–2, which decreased to 24 kgf mm^–2 at 20 vol%.     

Reversible Ion‐Conducting Switch in a Novel Single‐Ion Supramolecular Hydrogel Enabled by Photoresponsive Host–Guest Molecular Recognition

A novel ion‐conducting supramolecular hydrogel with reversible photoconductive properties in which the azobenzene motif, α‐cyclodextrin (α‐CD), and ionic liquid are grafted onto the gel matrix is reported. Host–guest interactions with different association constants between α‐CD and azobenzene or the anionic part of the ionic liquid can be readily tuned by photoinduced trans–cis isomerization of the azobenzene unit. When irradiated by 365 nm light, α‐CD prefers to form a complex with the anionic part of the ionic liquid, resulting in decreased ionic mobility and thus high resistance of the hydrogel. However, under 420 nm light irradiation, a more stable complex is again formed between α‐CD and trans‐azobenzene, thereby releasing the bound anions to regenerate the low‐resistive hydrogel. As such, remote control of the ionic conductivity of the hydrogel is realized by simple host–guest chemistry. With the incorporation of a logic gate, this hydrogel is able to reversibly switch an electric circuit on and off by light irradiation with certain wavelengths. The concept of photoswitchable ionic conductivity of a hydrogel mediated by competitive molecular recognition is potentially promising toward the fabrication of optoelectronic devices and applications in bioelectronic technology.     

Influence of the stretching temperature on an alumina filled microporous high density polyethylene membrane

The effects of the stretching temperature on the properties of an alumina filled high density polyethylene (HDPE) membrane were investigated. As the stretching temperature increases up to 120 °C, the porosities of the alumina filled HDPE membrane were increased. The crystallinity of the microporous alumina filled HDPE membranes was increased steadily with an increasing stretching temperature up to 120 °C. The pores of the alumina filled HDPE film was easily formed at the interface between the alumina particles and HDPE, and the lamellae separation of HDPE was enhanced as the crystallinity of the alumina filled HDPE film was increased. The tensile strength at a stretching temperature of 80 °C was a little larger than those at a stretching temperature of 100 °C and 120 °C. The electrolyte uptake and the ionic conductivity were increased in proportion to the porosity. When the stretching temperature was 120 °C, the ionic conductivity of the microporous alumina filled HDPE membrane reached 4.56 × 10⁻³ S/cm.     

Electrical properties of γ-CuCl thin films

The electrical properties of thin film CuCl, a wide band gap material with potential applications in the optoelectronic industry, has been studied using admittance spectroscopy in the frequency range 10 mHz–1 MHz and temperature range 280–400 K. The electrical conductivity of CuCl films was found to be mainly ionic and the temperature dependency follows the Arrhenius relationship. The power-law exponent of the AC dispersive regimes was found to be almost temperature independent. Further to this, DC electronic hole conductivity of the order of 2.3 × 10⁻⁷ S/cm was deduced to be in coexistence with Cu⁺ ionic conductivity using irreversible electrodes (Au), while a total conductivity of the order of 6.5 × 10⁻⁷ S/cm was obtained using reversible electrodes (Cu) at room temperature.     

Ionic conductivity of synthetic analcime,sodalite and offretite

The ionic conductivity of pressed pellets of dehydrated synthetic analcime, sodalite and offretite was determined by a.c. measurements within the range 10 Hz to 10 MHz. The ionic conductivity values of those zeolites exchanged with various monovalent cations were determined by the complex impedance plane method. The conduction activation energies range between 63 and 101 kJ mol^–1. Sodium analcime shows the best ionic conductivity, namely 1.8×10^–4–1 cm^–1 at 400° C. A comparison with the conductivity of other ion-conducting solids was made.     

Polymer electrolyte based dye-sensitized solar cell with rice starch and 1-methyl-3-propylimidazolium iodide ionic liquid

Biodegradable rice starch was used to prepare solid polymer electrolytes (SPEs) using sodium iodide salt. The polymer electrolytes are prepared using solution cast technique. 1-methyl-3-propylimidazolium iodide (MPII) ionic liquid was incorporated in the polymer electrolyte. The ionic conductivity of SPEs are measured and temperature-dependent behavior of SPEs studied. All the solid polymer electrolytes follow Arrhenius type of thermal activated model. The ionic conductivity increased after addition of MPII ionic liquid. The highest ionic conductivity of 1.20 × 10^− 3 S cm^− 1 is achieved upon addition of 20 wt.% of MPII ionic liquid. Structural properties of polymer electrolytes are studied with FTIR and XRD which confirmed complexation between polymer and ionic liquid. The polymer electrolytes are analyzed for thermal study using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Dye-sensitized solar cells (DSSC) are fabricated using polymer electrolytes and studied under Sun simulator. The highest energy conversion efficiency of 2.09% is attained after addition of 20 wt.% of MPII ionic liquid.     

Layered and interfacially blended polyelectrolyte multi-walled carbon nanotube composites for enhanced ionic conductivity

To enhance the ionic conductivity in solid phase polyelectrolyte systems for lithium ion battery applications demands effective control of the phase properties. Here, we report on a strategy involving a layer-by-layer methodology of two polyelectrolytes, poly(ethylene oxide) (PEO) and poly(acrylic) acid (PAA) and carboxylic acid functionalized multi-walled carbon nanotubes (MWNTs). Optimization of the assembly strategy revealed that undoped and lithium-ion doped stacking of four layers provides excellent film growth and improvement of the ionic conductivity of up to 10^− 5 S cm^− 1, which exceeds conventional assemblies of lithium-ion doped [PEO/PAA] by up to two orders of magnitude. Although ionic conductivity was most effectively enhanced for ultrathin films (< 100 nm), [PEO/PAA/PEO/(PAA + MWNT)] stacking still provides an ionic conductivity of > 10^− 6 S cm^− 1 for thick films (> 2 μm). The improvement of ionic conductivity was attributed to (i) interfacial phase mixing (blending) of the two polyelectrolytes, (ii) the MWNT contribution in the interfacial region, and (iii) the preferential adsorption of lithium-ions along the carbon nanotubes. This study involved a series of scanning probe methods including lateral force microscopy, and electrostatic force microscopy.     

Ionic transport in P(VdF-HFP)-PEO based novel microporous polymer electrolytes

A novel microporous polymer electrolyte (MPE) comprising blends of poly(vinylidene fluoride-cohexafluoropropylene) [P(VdF-HFP)] and polyethylene oxide (PEO) was prepared by phase inversion technique. It was observed that addition of PEO improved the pore configuration, such as pore size, pore connectivity and porosity of P(VdF-HFP) based membranes. The room temperature ionic conductivity was significantly enhanced. The highest porosity of about 65% and ionic conductivity of about 7 × 10⁻⁴ S cm⁻¹ was obtained when the weight ratio of PEO was 40%. The liquid electrolyte uptake was found to increase with increase in porosity and pore size. However, at higher weight ratio of PEO (> 40%) porosity, pore size and ionic conductivity was decreased. This descending trend with further increase of PEO weight ratio was attributed to conglomeration effect of PEO at the pores.     

Ionic conductivity of electrolytes formed from PEO-LiCF3SO3 complex low molecular weight poly(ethylene glycol)

Films of poly(ethylene oxide)-LiCF₃SO₃-based complexes containing different amounts of poly(ethylone glycol) (PEG) with molecular weights ranging from 400 to 2000 were prepared by solution casting. The ionic conductivity is presented as a function of temperature, molecular weight and the PEG content used. The conductivity increases with decreasing molecular weight of PEG and with increasing PEG content. The incorporation of PEG with a molecular weight of 600 or less gives rise to a maximum conductivity value of 3 × 10^–3 Sm^–1 at 25° C. The conductivity enhancement at room temperature can be attributed to the increase in the amorphous regions responsible for the ionic conduction.     

AC impedance and dielectric spectroscopic studies of Mg<Superscript>2 + </Superscript> ion conducting PVA–PEG blended polymer electrolytes

Polyvinyl alcohol (PVA)–polyethylene glycol (PEG) based solid polymer blend electrolytes with magnesium nitrate have been prepared by the solution cast technique. Impedance spectroscopic technique has been used, to characterize these polymer electrolytes. Complex impedance analysis was used to calculate bulk resistance of the polymer electrolytes. The a.c.-impedance data reveal that the ionic conductivity of PVA–PEG–Mg(NO₃)₂ system is changed with the concentration of magnesium nitrate, maximum conductivity of 9·63 × 10^− 5 S/cm at room temperature was observed for the system of PVA–PEG–Mg(NO₃)₂ (35–35–30). However, ionic conductivity of the above system increased with the increase of temperature, and the highest conductivity of 1·71 × 10^− 3 S/cm was observed at 100°C. The effect of ionic conductivity of polymer blend electrolytes was measured by varying the temperature ranging from 303 to 373 K. The variation of imaginary and real parts of dielectric constant with frequency was studied.     

Low temperature synthesis of Ga-doped Li7 La3 Zr2 O12 garnet-type solid electrolyte by mechanical method

Synthesis of Li_6.25 Ga_0.25 La₃ Zr₂ O₁₂ (LLZO-Ga) solid electrolyte powder granule for all solid-state battery was investigated by applying mechanical processing of the raw powder materials adding LiF-BaF₂ as a flux. The LLZO-Ga of highly crystalline was synthesized by the mechanical method using an attrition-type mill without any extra-heat assistance. When 10 mass% of LiF-BaF₂ was added to the raw powder materials and 28 min processed, LLZO-Ga powder was favorably synthesized and granulated at the chamber temperature of 284 °C. The ionic conductivity of the sintered body of the LLZO-Ga granules was evaluated by impedance measurement. It revealed the high ionic conductivity of σ_total 1.0 × 10⁻³ S/cm. It suggests that the formation of LLZO-Ga/BaZrO₃ grain boundary contributes to higher ionic conductivity adding to the high crystalline phase of LLZO-Ga.     

DSC and conductivity studies on PVA based proton conducting gel electrolytes

An attempt has been made in the present work to prepare polyvinyl alcohol (PVA) based proton conducting gel electrolytes in ammonium thiocyanate (NH₄SCN) solution and characterize them. DSC studies affirm the formation of gels along with the presence of partial complexes. The cole-cole plots exhibit maximum ionic conductivity (2.58 × 10⁻³ S cm⁻¹) for gel samples containing 6 wt% of PVA. The conductivity of gel electrolytes exhibit liquid like nature at low polymer concentrations while the behaviour is seen to be affected by the formation of PVA-NH₄SCN complexes upon increase in polymer content beyond 5 wt%. Temperature dependence of ionic conductivity exhibits VTF behaviour.     

PAN–PEO solid polymer electrolytes with high ionic conductivity

The transparent and flexible solid polymer electrolytes (SPEs) are fabricated from polyacrylonitrile–polyethylene oxide (PAN–PEO) copolymer. The formation of the copolymer is confirmed by Fourier-transform infrared spectroscopy (FTIR) and Gel permeation chromatography (GPC) measurements. The effects of acrylonitrile (AN) wt% content and M_n(PEO) on ionic conductivity are investigated by alternating current (ac) impedance spectroscopy. By controlling and adjusting the AN wt% content and doping PEO with high molecular weight, the ionic conductivity of SPEs is optimized. The ionic conductivity of PAN–PEO solid polymer electrolytes is found to be high 6.79 × 10⁻⁴ S cm⁻¹ at 25 °C with an [EO]/[Li] ratio of about 10, and are electrochemically stable up to about 4.8 V versus Li/Li⁺. The conductivity and interfacial resistance remain almost constant even at 80 °C.     

Designing Optimal Perovskite Structure for High Ionic Conduction

Solid-oxide fuel/electrolyzer cells are limited by a dearth of electrolyte materials with low ohmic loss and an incomplete understanding of the structure–property relationships that would enable the rational design of better materials. Here, using epitaxial thin-film growth, synchrotron radiation, impedance spectroscopy, and density-functional theory, the impact of structural parameters (i.e., unit-cell volume and octahedral rotations) on ionic conductivity is delineated in La_0.9Sr_0.1Ga_0.95Mg_0.05O_3–δ. As compared to the zero-strain state, compressive strain reduces the unit-cell volume while maintaining large octahedral rotations, resulting in a strong reduction of ionic conductivity, while tensile strain increases the unit-cell volume while quenching octahedral rotations, resulting in a negligible effect on the ionic conductivity. Calculations reveal that larger unit-cell volumes and octahedral rotations decrease migration barriers and create low-energy migration pathways, respectively. The desired combination of large unit-cell volume and octahedral rotations is normally contraindicated, but through the creation of superlattice structures both expanded unit-cell volume and large octahedral rotations are experimentally realized, which result in an enhancement of the ionic conductivity. All told, the potential to tune ionic conductivity with structure alone by a factor of ≈2.5 at around 600 °C is observed, which sheds new light on the rational design of ion-conducting perovskite electrolytes.     

Ion conducting properties of hydrogen-containing Ta2O5 thin films prepared by reactive sputtering

Hydrogen-containing Ta₂O₅ (Ta₂O₅:H) thin films are considered to be a candidate for a proton-conducting solid-oxide electrolyte. In this study, Ta₂O₅:H thin films were prepared by reactively sputtering a Ta metal target in an O₂ + H₂O mixed gas. The effects of sputtering power and post-deposition heat treatment on the ion conducting properties of the Ta₂O₅:H thin films were studied. The ionic conductivity of the films was improved by decreasing the RF power and a maximum conductivity of 2 × 10⁻⁹ S/cm was obtained at an RF power of 20 W. The ionic conductivity decreased by heat-treatment in air, and no ion-conduction was observed after treatment at 300 °C due to the decrease in hydrogen content in the films.     

Electrical Conductivity of AlN-Mg<Subscript>3</Subscript>N<Subscript>2</Subscript> Solid Solutions

AlN-Mg₃N₂ solid solutions are synthesized, and their electrical conductivity and ionic transference number are measured. In the range 500–1150°C, the conductivity of the solid solutions increases with Mg₃N₂ concentration. The ionic transference number is close to unity, and the ionic transport is mainly due to aluminum ions.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 819–822.Original Russian Text Copyright © 2005 by Lesunova, Burmakin.     

Improved ohmic contacts on pentacene based on Au with ultraviolet irradiation treatment

The effect of ultraviolet irradiation treatment on a reduction in contact resistivity at the pentacene/Au interfaces was investigated using current-voltage and X-ray photoelectron spectroscopy in this study. The contact resistivity was drastically decreased from 2.2 × 10⁷ to 9.5 × 10² Ω cm² by the treatment. We suggested that the lower contact resistivity of the pentacene/Au sample with ultraviolet irradiation treatment than the pentacene/Au sample without ultraviolet irradiation treatment may be attributed to the heightened conductivity of pentacene near the pentacene/Au interface resulting from the incorporation of oxygen (from the Au surfaces with ultraviolet irradiation treatment) in pentacene near the interface.     

Preparation of PVDF/PMMA blend microporous membranes for lithium ion batteries via thermally induced phase separation process

Thermally induced phase separation (TIPS) process was employed to prepare microporous poly (vinylidene fluoride)/poly (methyl methacrylate) (PVDF/PMMA) blend membranes using sulfolane as the diluent. Then they were immersed in liquid electrolyte to form polymer electrolytes. The effect of PMMA on the morphology and the crystallinity of blend membranes was studied. It was found that phase separation between PVDF and PMMA occurred when PMMA content was 40 wt.%. The addition of PMMA increased porosity and decreased the crystallinity, which in turn enhanced electrolyte uptake of blend membrane and the ionic conductivity of corresponding polymer electrolyte. The maximum ionic conductivity was 2.45 × 10^− 3Scm^− 1 at 20 °C.     

Sputter deposited LiPON thin films from powder target as electrolyte for thin film battery applications

Lithium phosphorus oxynitride (LiPON) thin films as solid electrolytes were prepared by reactive radio frequency (rf) magnetron sputtering from Li₃PO₄ powder compact target. High deposition rates and ease of manufacturing powder target compared with conventional ceramic Li₃PO₄ targets offer flexibility in handling and reduce the cost associated. Rf power density varied from 1.7 Wcm^− 2 to 3 Wcm^− 2 and N₂ flow from 10 to 30 sccm for a fixed substrate to target distance of 4 cm for best ionic conductivity. The surface chemical analysis done by X-ray photoelectron spectroscopy showed incorporation of nitrogen into the film as both triply, N_t and doubly, N_d coordinated form. With increased presence of N_t, ionic conductivity of LiPON was found to be increasing. The electrochemical impedance spectroscopy of LiPON films confirmed an ionic conductivity of 1.1 × 10^− 6 Scm^− 1 for optimum rf power and N₂ flow conditions.