Conductivity studies on chitosan/PEO blends with LiTFSI salt

Chitosan/PEO-LiTFSI films have been prepared by the solution cast technique. The highest conductivity at room temperature was 1.4 × 10⁻⁶ Scm⁻¹ and the activation energy was 0.47 eV for chitosan/PEO blends containing 30 wt.% LiTFSI salts. The conductivity of the samples is dependent on the number of mobile ions. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Electrical conductivity studies on PVA/PVP-KOH alkaline solid polymer blend electrolyte

A series of conducting thin-film solid electrolytes based on poly (vinyl alcohol)/ poly (vinyl pyrrolidone) (PVA/PVP) polymer blend was prepared by the solution casting technique. PVA and PVP were mixed in various weight percent ratios and dissolved in 20 ml of distilled water. The samples were analyzed by using impedance spectroscopy in the frequency range between 100 Hz and 1 MHz. The PVA/PVP system with a composition of 80% PVA and 20 wt.% PVP exhibits the highest conductivity of (2.2±1.4) × 10⁻⁷ Scm⁻¹. The highest conducting PVA/PVP blend was then further studied by adding different amounts of potassium hydroxide (KOH) ionic dopant. Water has been used as solvent to prepare PVA/PVP-KOH based alkaline solid polymer blend electrolyte films. The conductivity was enhanced to (1.5 ± 1.1) × 10⁻⁴ Scm⁻¹ when 40 wt.% KOH was added. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Ionic conductivity studies of 49% poly(methyl methacrylate)-grafted natural rubber-based solid polymer electrolytes

The potential of 49% poly(methyl methacrylate)-grafted natural rubber (MG49) as a solid polymer electrolyte film in rechargeable batteries system were explored. The flat, thin, and flexible films were prepared by solution casting technique. The ionic conductivity was investigated by alternating current impedance spectroscopy. The highest conductivity of 2.3 × 10⁻⁷ Scm⁻¹ was obtained at 20wt.% of LiBF₄ salts content, while 4.0 × 10⁻⁸ Scm⁻¹ was obtained at 15wt.% LiClO₄ salts loading. The observation on structure performed by X-ray diffraction shows the highest conductivity appears at amorphous phase.     

Transport mechanism of Cu-ion conducting PVA based solid-polymer electrolyte

Copper-ion conducting solid-polymer electrolyte systems based on Polyvinyl alcohol (PVA) has been prepared by solution cast technique. UV-VIS data show a broad peak in the wavelength region 600–800 nm due to complex formation. The 30 wt.% Cu(NO₃)₂ doped system has a maximum conductivity of 1.6×10⁻⁵ Scm⁻¹ at room temperature. The conductance spectrum shows two distinct regions: a dc plateau and a dispersive region. The dielectric spectra show an increase in the dielectric constant with decreasing frequency. The transference number measurements reveal that the transport in these electrolytes is mainly due to ions. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Combined effect of CuO nanofillers and DBP plasticizer on ionic conductivity enhancement in the solid polymer electrolyte PEO–LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript>

We report a new kind of polyethylene oxide, PEO–LiCF₃SO₃-based composite polymer electrolyte, containing active copper oxide (CuO) nanoparticles with dibutyl phthalate (DBP) prepared by solution-cast technique. The incorporation of 10 wt.% DBP and 5 wt.% CuO to the salted polymer showed a significant conductivity enhancement with maximum conductivity 2.62 × 10⁻⁴ Scm⁻¹ at room temperature. This could be attributed to the increasing of amorphous phase content and structural changes in the polymer electrolyte. Arrhenius plot suggest that temperature-dependent conductivity is a thermally activated process.     

Ionic conductivity studies of chitosan-based polymer electrolytes doped with adipic acid

Chitosan acetate–adipic acid film polymer electrolytes have been prepared by the solution cast technique. The highest conductivity is 1.4 × 10⁻⁹ S cm⁻¹ for 35 wt.% of adipic acid at room temperature. The sample with highest conductivity has the lowest activation energy. Calculations using the Rice and Roth model provide number of mobile ions, η. The conductivity is dependent on the diffusion coefficient and mobility.     

An investigation of the morphological, electrical and optoelectronic properties of short chain Di-ureasils doped with Er3+ ions

Hybrid organic/inorganic xerogels containing Er³⁺ ions have been prepared by the solgel process. The hybrid framework of these compounds, designated as di-ureasils and represented by U(600), is composed of a siliceous backbone to which polyether chains containing 8.5 oxyethylene repeat units are linked through urea (-NHC(=O)NH-) bridges. The trivalent cations have been incorporated in the matrix as erbium triflate, Er(CF₃SO₃)₃. Compositions with n (where n is the molar ratio of (OCH₂CH₂) repeat units per Er⁺ ion) between ∞ and 3 have been studied. The morphology of the materials was characterized by means of X-ray Diffraction and Differential Scanning Calorimetry. Complex Impedance spectroscopy was used to evaluate the levels of conductivity exhibited by the xerogels as a function of temperature. The results obtained clearly demonstrate the amorphous character of the samples analysed. At about 100 °C the most conducting sample is U(600)₅Er(CF₃SO₃)₃ (approximately 2×10⁻⁵ Scm⁻¹), whereas the U(600)₆₀Er(CF₃SO₃)₃ compound displays the highest conductivity at room temperature (1×10⁻⁷ Scm⁻¹). We have shown that concentration effects on the quenching of the 1.53 μm emission intensity (excited at 488 nm) are negligible. We have also shown that the Er³⁺ ions are active at room temperature. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

D.C. conductivity of transparent conductive ZnO:Al films in the temperature range 80–360 K

An experimental study of the temperature dependence of the d.c. conductivity σ as a function of temperature T in the range from 80–360 K on nanocrystalline ZnO:Al films (Al³⁺ 2%) of thickness 500 nm prepared on glass microscope slides by a dip — coating method is presented. The electrical conductivity σ, which at room temperature varied between 0.1 to 2.7 S/cm, increased almost linearly with T for all the samples. Measurements of the Hall coefficient at room temperature and in a magnetic field of 1.2 T, gave R_H=0.53 cm³C⁻¹, from which a carrier concentration of n=1.18×10¹⁹ cm⁻³ and a carrier mobility of μ=1.40 cm²/Vs were deduced. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14–18, 2004.     

Effect of ZnO nanoparticles filler concentration on the properties of PEO-ENR50-LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript> solid polymeric electrolyte

A solid polymer electrolyte comprising blend of poly(ethylene oxide) and 50% epoxidized natural rubber (ENR50) as a polymer host, LiCF₃SO₃ as a salt and nanoparticle ZnO as an inorganic filler was prepared by solution-casting technique. The effect of filler on the electrolyte properties was characterized and analysed. FESEM analysis showed that the filler was well distributed in the polymer matrix, while the effective interaction between the salt and the polymer host was reduced by the addition of filler. As evidenced by FTIR analysis, which showed the formation of triplet peak at C-O-C stretching region. Ionic conductivity was found to decrease from 1.4 × 10⁻⁴ Scm⁻¹ to 2.5 × 10⁻⁶ Scm⁻¹ upon the addition of filler, due to the blocking effect of filler into the electrolyte conduction pathways. The temperature dependence on the electrolyte conductivity obeys Arrhenius rule in two temperature regions.     

Electrical properties of a solid polymeric electrolyte of PVC–ZnO–LiClO4

The ZnO filler has been introduced into a solid polymeric electrolyte of polyvinyl chloride (PVC)–ZnO–LiClO₄, replacing costly organic filler for conductivity improvement. Ionic conductivity of PVC–ZnO–LiClO₄ as a function of ZnO concentration and temperature has been studied. The electrolyte samples were prepared by solution casting technique. The ionic conductivity was measured using impedance spectroscopy technique. It was observed that the conductivity of the electrolyte varies with ZnO concentration and temperature. The temperature dependence on the conductivity of electrolyte was modelled by Arrhenius and Vogel–Tammann–Fulcher equations, respectively. The temperature dependence on the conductivity does not fit in both models. The highest room temperature conductivity of the electrolyte of 3.7 × 10⁻⁷ Scm⁻¹ was obtained at 20% by weight of ZnO and that without ZnO filler was found to be 8.8 × 10⁻¹⁰ Scm⁻¹. The conductivity has been improved by 420 times when the ZnO filler was introduced into the PVC–LiClO₄ electrolyte system. It was also found that the glass transition temperature of the electrolyte PVC–ZnO–LiClO₄ is about the same as PVC–LiClO₄. The increase in conductivity of the electrolyte with the ZnO filler was explained in terms of its surface morphology.     

Dielectric and conductivity relaxations in PVAc based polymer electrolytes

The polymer electrolytes composed of a blend of poly (vinyl acetate) (PVAc) and poly (methylmethacrylate) (PMMA) as a host polymer and LiClO₄ as a salt are prepared by a solution casting technique. The formation of blend polymer- salt complex has been confirmed by FT-IR spectral studies. The conductivity- temperature plots are found to follow an Arrhenius nature. Arrhenius plot shows the decrease in activation energy with the increase in salt concentration. The dielectric behaviour of the sample is analysed using dielectric permittivity (ε′), dielectric loss (ε″) and electric modulus (M″) of the samples. The impedance cole- cole plot shows the high frequency semi- circle is due to the bulk effect of the material and the depression in the semicircle shows the non-Debye nature of the material. The bulk conductivity is found to vary between 2.5×10⁻⁵ Scm⁻¹ to 1.7×10⁻³ Scm⁻¹ with the increase of salt concentration of blend polymer samples. The migration energy derived from the dissipation factor is almost equal to the activation energy calculated from conductivity. The modulus spectrum of the samples shows the non-Debye behaviour of the polymer electrolyte films. The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Structural and ionic conductivity studies on proton conducting polymer electrolyte based on polyvinyl alcohol

An attempt has been made to prepare a new proton conducting polymer electrolyte based on polyvinyl alcohol (PVA) doped with NH₄NO₃ by solution casting technique. The complex formation between polymer and dissociated salt has been confirmed by X-ray diffraction analysis. The ionic conductivity of the prepared polymer electrolyte has been found by ac impedance spectroscopic analysis. The highest ionic conductivity has been found to be 7.5 × 10⁻³ Scm⁻¹ at ambient temperature for 20 mol% NH₄NO₃-doped PVA with low activation energy (~0.19 eV). The temperature-dependent conductivity of the polymer electrolyte follows an Arrhenius relationship, which shows hopping of ions in the polymer matrix.     

Morphology,chemical interaction,and conductivity of a PEO-ENR50 based on solid polymer electrolyte

A solid polymer electrolytes (SPE) comprising blend of poly(ethylene oxide; PEO) and epoxidized natural rubber as a polymer host and LiCF₃SO₃ as a dopant were prepared by solution-casting technique. The SPE films were characterized by field emission scanning electron microscopy to determine the surface morphology, X-ray diffraction, and differential scanning calorimeter to determine the crystallinity and thermogravimetric analysis to confirm the mass decrease caused by loss of the solvent. While the presence of the complexes was investigated by reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Electrochemical impedance spectroscopy was conducted to obtain ionic conductivity. Scanning electron microscopy analysis showed that a rough surface morphology of SPE became smoother with addition of salt, while ATR-FTIR spectroscopy analysis confirmed the polymer salt complex formation. The interaction occurred between the salt, and ether group of polymer host where the triple peaks of ether group in PEO merged and formed one strong peak at 1,096 cm⁻¹. Ionic conductivity was found to increase with the increase of salt concentration in the polymer blend complexes. The highest conductivity achieved was 1.4 × 10⁻⁴ Scm⁻¹ at 20 wt.% of LiCF₃SO₃, and this composition exhibited an Arrhenius-like behavior with the activation energy of 0.42 eV and the preexponential factor of 1.6 × 10³ Scm⁻¹.     

Effect of ethylene carbonate plasticizer and TiO<Subscript>2</Subscript> nanoparticles on 49% poly(methyl methacrylate) grafted natural rubber-based polymer electrolyte

The effect of plasticizer and TiO₂ nanoparticles on the conductivity, chemical interaction and surface morphology of polymer electrolyte of MG49–EC–LiClO₄–TiO₂ has been investigated. The electrolyte films were successfully prepared by solution casting technique. The ceramic filler, TiO₂, was synthesized in situ by sol-gel process and was added into the MG49–EC–LiClO₄ electrolyte system. Alternating current electrochemical impedance spectroscopy was employed to investigate the ionic conductivity of the electrolyte films at 25 °C, and the analysis showed that the addition of TiO₂ filler and ethylene carbonate (EC) plasticizer has increased the ionic conductivity of the electrolyte up to its optimum level. The highest conductivity of 1.1 × 10⁻³ Scm⁻¹ was obtained at 30 wt.% of EC. Fourier transform infrared spectroscopy measurement was employed to study the interactions between lithium ions and oxygen atoms that occurred at carbonyl (C=O) and ether (C-O-C) groups. The scanning electron microscopy micrograph shows that the electrolyte with 30 wt.% EC posses the smoothest surface for which the highest conductivity was obtained.     

Electrical and photoelectrical studies of plasma polymerized acrylonitrile

The electrical and photoelectrical properties of plasma polymerized acrylonitrile (PAN) are reported. The polymer films were studied in silver-PAN-silver systems. Electrical conductivity at room temperature was of the order of 10⁻¹¹ ohm⁻¹ cm⁻¹. The space charge limited current (SCLC) studies at room temperature and thermally stimulated current studies (TSC) over a temperature range of 290–500°K led to a clear understanding of carrier concentration, carrier mobility, trapping levels and activation energies. Photoelectric measurements were used to draw a band picture in plasma depositedPAN.     

Preparation and characterizations of PVAc/P(VdF-HFP)-based polymer blend electrolytes

A novel group of polymer blend electrolytes based on the mixture of poly(vinyl acetate) (PVAc), poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP), and the lithium salt (LiClO₄) are prepared by solvent casting technique. Ionic conductivity of the polymer blend electrolytes has been investigated by varying the PVAc and PVdF-HFP content in the polymer matrix. The maximum ionic conductivity has been obtained as 0.527 × 10⁻⁴ Scm⁻¹ at 303 K for PVAc/PVdF-HFP ((25/75) wt.%)/LiClO₄ (8 wt.%). The complex formations ascertained from XRD and FTIR spectroscopic techniques and the thermal behavior of the prepared samples has been performed by DSC analysis. The surface morphology and the surface roughness are studied using SEM and AFM scanning techniques respectively.     

Solid polymeric electrolyte of PVC–ENR–LiClO<Subscript>4</Subscript>

The ionic conductivity of PVC–ENR–LiClO₄ (PVC, polyvinyl chloride; ENR, epoxidized natural rubber) as a function of LiClO₄ concentration, ENR concentration, temperature, and radiation dose of electron beam cross-linking has been studied. The electrolyte samples were prepared by solution casting technique. Their ionic conductivities were measured using the impedance spectroscopy technique. It was observed that the relationship between the concentration of salt, as well as temperature, and conductivity were linear. The electrolyte conductivity increases with ENR concentration. This relationship was discussed using the number of charge carrier theory. The conductivity–temperature behaviour of the electrolyte is Arrhenian. The conductivity also varies with the radiation dose of the electron beam cross-linking. The highest room temperature conductivity of the electrolyte of 8.5 × 10⁻⁷ S/cm was obtained at 30% by weight of LiClO₄. The activation energy, E _a and pre-exponential factor, σ _o, are 1.4 × 10⁻² eV and 1.5 × 10⁻¹¹ S/cm, respectively.     

Effects of gamma radiation treatment and plasticizer on alkaline solid polymer electrolytes

Alkaline solid polymer electrolyte films have been prepared by the solvent-casting method. Gamma radiation treatment and propylene carbonate plastisizer were used to improve the ionic conductivity of the electrolytes at ambient temperature. The structure of the irradiated electrolytes changes from semi-crystalline to amorphous, indicating that the crosslinking of the polymer has been achieved at a dose of 200 kGy. The ionic conductivity at room temperature of PVA/KOH blend increases from 10⁻⁷ to 10⁻³ Scm⁻¹ after the PVA crosslinking and when the plasticizer concentration was increased from 20 to 30%. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Ionic conductivity studies on LiSmO<Subscript>2</Subscript> by impedance spectroscopy

Lithium samarium oxide has been prepared by solid-state reaction method and characterized by X-ray diffraction (XRD) and impedance spectroscopy. XRD pattern of the sample reveals the formation of the sample. The conductivity studies, dielectric studies, and modulus analysis of the samples have been carried out for different temperatures. The bulk conductivity of the sample has been found to be 1.21 × 10⁻⁵ Scm⁻¹ at 420 °C. The temperature variation of the direct current conductivity obeys the Arrhenius relation. The modulus analysis of the sample indicates the non-Debye nature of the sample which corresponds to long-time slow polarization and relaxation of hopping charges.     

Raman scattering in a near-surface n-GaAs layer implanted with boron ions

Structure in the Raman scattering spectra of near-surface n-GaAs layers (n=2×10¹⁸ cm⁻³) implanted with 100 keV B⁺ ions in the dose range 3.1×10¹¹–1.2×10¹⁴ cm⁻² is investigated. The qualitative and quantitative data on the carrier density and mobility and on the degree of amorphization of the crystal lattice and the parameters of the nanocrystalline phase as a result of ion implantation are obtained using a method proposed for analyzing room-temperature Raman spectra. Fiz. Tverd. Tela (St. Petersburg) 41, 1495–1498 (August 1999)