Structural, thermal and electrical properties of PVA-LiCF3SO3 polymer electrolyte

The development of polymeric systems with high ionic conductivity is one of the main objectives in Li rechargeable battery. In the present study, the different composition of PVA-LiCF₃SO₃ polymer electrolyte has been prepared by solution cast technique using DMSO as solvent. The FTIR study confirms the polymer-salt complex formation. The amorphous nature of the polymer has been confirmed by XRD analysis. DSC measurements show decrease in T_g with increasing salt concentration. The temperature dependent conductivity obeys Arrhenius relationship. The maximum conductivity has been observed in the order of 7 × 10^− 4 S cm^− 1 for 25 mol% of LiCF₃SO₃. The activation energy has been found to be 0.16 eV. The two peaks have been observed in the dielectric loss spectrum which shows two types of relaxation α and β.     

Conductivity and Optical Properties of a Polyiodine Canal Complex (Benzophenone)9(KI)2I7, CHCl3

Abstract

(Benzophenone)₉(KI)₂I₇, CHCl₃ single crystals have a golden metallic reflection on the surfaces parallel to the polyiodine chain axis. The compound is a member of a large class of channel-like inclusion compounds in which isolated iodine atom chains are the only possible conducting strands in an otherwise insulating matrix. The (contactless) microwave conductivity is ～ 10 Ω^?1 cm^?1 at room temperature with an activation energy of ～0.03 eV down to 70°K, while the dc conductivity is ～10^?-⁶. Conductivity is strongly frequency dependent and contact problems are severe.     

Addition effects of bismuth oxide on Samaria-doped ceria based lithium carbonate composite electrolytes for intermediate temperature-solid oxide fuel cells

ABSTRACT

The effect of amounts (3, 5, 10, 20 wt%) of Bi₂O₃ on the sintering characteristics and porosity of Samaria-doped Ceria (SDC) based Lithium carbonate has been evaluated. The density had a maximum as high as 98.5% of theoretical density at 800°C with only 1wt%Li₂CO₃ and 3 wt%Bi₂O₃. The composite electrolytes showed high ion conductivity at evaluated temperatures. Composition and calcination temperature were found to affect the morphology and conductivity of the composite electrolytes greatly. The total conductivity closed to 3 orders of magnitude greater than pure SDC at operating temperature of 900°C and 3.5 orders of magnitude greater than pure SDC at operating temperature of 600°C. Especially, the best sample containing 3 wt% Bi₂O₃ sintered at 800°C for 2 h which had an ionic electrical conductivity of 0.17S cm^?1. According to fuel cell performance, these composite electrolytes are chemically stable, which is an attractive prospect in intermediate temperature solid oxide fuel cell applications.     

The Effect of Plasticization on Conductivity and Other Properties of Starch/Chitosan Blend Biopolymer Electrolyte Incorporated with Ammonium Iodide

This work focuses on polymer electrolytes composed of a starch-chitosan blend host, ammonium iodide (NH₄I) and glycerol. Fourier transform infrared (FTIR) analysis confirms the interaction of starch-chitosan-NH₄I-glycerol. The highest room temperature conductivity is (1.28 ± 0.07) × 10^?3 S cm^?1, obtained by a sample containing 30 wt% glycerol. Dielectric studies showed that the electrolytes obeyed non-Debye behavior. The total ionic transference number for the 30 wt% glycerol sample was 0.991, and the conduction mechanism for this sample followed the quantum mechanical tunneling (QMT) model. Linear sweep voltammetry (LSV) showed that this sample was electrochemically stable up to 1.90 V. The highest conducting sample was used in the fabrication of an electrical double layer capacitor (EDLC) cell.     

Growth and ionic conductivity of Li3 + x P1 − x GexO4 (x = 0.34) single crystals

Li_{3 + x} P_{1 ? x} Ge_xO₄ crystals (x = 0.34) with dimensions of about 3 × 3 × 5 mm³ were grown for the first time from flux. The conductivities of the crystals measured along three directions have close values and are equal to σ ≈ 1.8 × 10^?6 and 3.7 × 10^?2 Sm/cm at the temperatures 40 and 400°C, respectively (similar to the case of pure lithium phosphate, somewhat lower values of electric conductivity were measure along the b axis). The activation energy of conductivity is equal to 0.54 eV. A considerable increase in the conductivity of the solid solution in comparison with the conductivity of pure lithium phosphate is explained by the specific features of the lithium sublattice in the crystal structure of the λ-Li₃PO₄ type.     

Ionic conductivity of Li2OB2O3 thin films

The ionic conductivity of evaporated Li₂OB₂O₃ thin films has been studied. These thin films were found to show a considerably high ionic conductivity of 1 × 10^?7 Ω^?1 cm^?1 at room temperature. The conductivity increases with increasing Li content and exhibits a maximum value near 3Li₂O·B₂O₃. The structure of these films was determined using infrared absorption and laser Raman scattering spectroscopy. Using the results, the correlation between structure and conductivity is also discussed.     

Exploration on nano-composite fumed silica-based composite polymer electrolytes with doping of ionic liquid

Fumed silica (SiO₂)-based composite polymer electrolytes were prepared by means of solution casing technique. Horizontal attenuated total reflectance-Fourier Transform Infrared (HATR-FTIR) study shows the complexation between polymer matrix and SiO₂. The highest ionic conductivity of (4.11 ± 0.01) × 10^? 3 Scm^? 1 is achieved upon inclusion of 8 wt.% of SiO₂. Three different regions have been observed in the frequency dependence–ionic conductivity study. The conductivity rises sharply with frequency at low frequency regime. It is followed by a frequency independent plateau region and sharp decrease in the conductivity at high frequency range. The dielectric permittivity (ε^') and dielectric loss (ε^") are decreased with increasing the frequency. This phenomenon is mainly attributed to the electrode polarization effect. The formation of electrical double layer has been proven in these dielectric permittivity studies. This indicates the non-Debye properties of the nano-composite polymer electrolytes.     

Electrochemical characterizations and the effect of glycerol in biopolymer electrolytes based on methylcellulose-potato starch blend

ABSTRACT

Polymer electrolytes have been prepared by blending methylcellulose (MC)-potato starch, doped with lithium perchlorate (LiClO₄) and plasticized with glycerol. The blend of 60 wt% MC-40 wt% starch was found to be the most suitable ratio to serve as polymer host. Fourier transform infrared (FTIR) spectroscopy analysis proved the interaction among the components. X-ray diffraction (XRD) analysis indicated that the conductivity enhancement is due to the increase in amorphous content. The highest ionic conductivity obtained at room temperature was (4.25 ± 0.82) × 10^?4 S cm^?1 for MC-starch-LiClO₄-20 wt% glycerol. The highest conducting samples in both systems were found to obey Arrhenius rule. Dielectric study further strengthens the conductivity result.     

The field effect in amorphous chalcogenides: An investigation of localized states and electronic transport

The temperature dependence of the field effect response permits an unambiguous determination of the identity of those states responsible for electrostatic screening in the amorphous chalcogenides. We observe (1) in As₂Te₃, field effect screening by localized states at the Fermi level at low temperatures (～ 10¹⁹ cm^?3 eV^?1) and by mobile charge carriers (～ 10¹⁸ cm^?3 at 300 K) at high temperatures, and a transition from p-type to two-carrier (primarily n-type) conductivity as the temperature is raised above ～320 K; (2) in As₂SeTe₂, screening by mobile charge carriers (～ 10¹⁸ cm^?3 at 300 K) with strongly type conductivity; (3) in As₂Se₂Te, screening by localized states at the Fermi level (～ 10¹⁹ cm^?3 eV^?1) with strongly p-type conductivity; and (4) in Sb₂Te₃, a very high density of localized states at the Fermi level (～ 2 × 10²⁰ cm^?3 eV^?1) with both electron and hole contributions to the conductivity. Correlation with thermoelectric power results suggests that the p-type conductivity in As₂Te₃ is due to near-equal contributions from two processes: hopping in localized states plus extended state conduction. Aging and annealing behavior is described with the aid of a “chaotic potential model” that appears to be able to account for large changes in mobile carrier density that leave the conductivity unaltered.     

Magnetic Resonance on (QP)4(SbF6)3, a Radical Cation Salt of P-Quaterphenylene

Abstract

The unit cell of (QP)₄(SbF₆)₃ shows triads of QP in an arene stack and one QP in the anion sheet. The sum formula is therefore (QP)₃QP(SbF₆)₃. Electron-electron repulsion force le^?/site resulting in a semi-conducting state. This is in agreement with an activated conductivity of max 10^?1 Scm^?1 at 300 K.

Magnitude and activation energy of the paramagnetic susceptibility do not coincide with those of the conductivity; spins and charges are localized and decoupled due to the strong alternation of distances within the cation stack. Spin diffusion along the stacks governs, at least above 180 K, the magnetic properties: narrow ESR-lines and proton spin relaxation via hyperfine interaction with the relaxation dispersion T ^?1 _1H α ω^?1/2 above 200 K.

A lower value for the intrachain exchange rate τ₁ ^?1> 8.10¹¹ sec^?1 and a lower limit of 10³ for the anisotropy can be evaluated.

Keywords: quaterphenylene, molecular crystal, radical cation salt, low dimensionality, magnetic resonance     

Ionic conductivity of the phases of five types formed in the BaF2-GdF3 system

The ionic conductivity has been measured in ceramic phases of five structure types found in the BaF₂-GdF₃ system: the fluorite type (CaF₂), its trigonal and tetragonal distortions, the tysonite type (LaF₃), and the orthorhombic ??-YF₃ modification. The phases have been obtained by solid-phase synthesis from BaF₂ and GdF₃ mixtures in hermetic nickel containers at 925, 964, and 1067°C for 108?C360 h in a fluorine atmosphere. Their conductivity ?? is compared in correlation with the composition and structure type. The highest conductivity values are found for the tysonite Gd_{1 ? y} Ba _y F_{3 ? y} phase (0.10 ?? y ?? 0.25): (1?2) × 10^?3 S/cm at 683 K. The ordered Ba_0.60Gd_0.40F_2.40 and Ba_0.57Gd_0.43F_2.43 phases with fluorite-derived structures and different degrees of order are characterized by the lowest conductivities: i(1.5?3.5 × 10^?5) S/cm.     

Study of amorphous Ge–SiO2–P+Si tunnel junctions

A new method to determine ac conductivity of amorphous Ge using Al-amorphous Ge–SiO₂–P⁺Si tunnel junctions is presented. Frequency dependence of ac conductivity is found to satisfy the power law in the frequency range between 1 and 50 kHz and the density of localized states at the Fermi level is estimated to be ～ 1.7 × 10²⁰ cm^?3 eV^?1 which decreases to ～ 4.5 × 10¹⁹ cm^?3 eV^?1 after annealing at 175°C.Temperature dependence of tunneling conductance of Al-amorphous Ge–SiO₂–P⁺Si junctions is appreciable only near zero bias. Zero bias conductance of the junctions obeys the $\text{T}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>4</mtext>}}$ law of Mott; the density of localized states obtained from the $\text{T}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>4</mtext>}}$ law is one order of magnitude smaller than that obtained by ac conductivity measurements, being insensitive to annealing. This behavior of the tunnel junctions differes in many respects from those of Al–Al₂O₃-amorphous Ge tunnel juntions.     

Influence of purity of NdF3 single crystals on their ionic conductivity

Single crystals of the NdF₃ superionic conductor have been grown by the Bridgman method from a melt in a helium atmosphere using a fluorinating PbF₂ agent. Commercial NdF₃ reagents of special purity grade, reagent grade, and pure grade are used. It is found that the ionic conductivity ?? of the crystals depends considerably on the purity grade of the starting substances: at 200°C ?? = 1.4 × 10^?, 3 × 10^?4, and 8 × 10^?4 S/cm for reagents of special purity grade, reagent grade, and pure grade, respectively.     

Phase states of the gypsum thermal-annealing derivatives according to electron spin resonance spectra

The electron spin resonance (ESR) spectra of SO ₃ ^? and SO ₂ ^? radical ions with a linewidth ΔH ≈ 2.7 G and SO ₃ ^? (A ₁) and SO ₃ ^? (A ₂) centers with superhyperfine splitting due to the interaction with protons in platelike gypsum single crystals under X-ray irradiation have been analyzed at 25°C. Dehydrated regions with a radius >4 Å are revealed in gypsum. The ESR spectra of SO ₃ ^? radical ions and atomic hydrogen with ΔH ≈ 0.3 G are found in the products of isothermal annealing of gypsum kept for 30 min after X-ray irradiation at 25°C. The dependences of the intensities of these spectra on the annealing temperature are studied in the range of 100–450°C. The temperature range of formation of α- and β-phase states of bassanite and γ-anhydrite are determined. The process of residual water redistribution between the channel systems of the α- and β-phase types of γ-CaSO₄ in gypsum thermal derivatives is established.     

Solution-Processable Low Voltage Organic Transistors of Thieno[3,2-b]thiophene-Based Conducting Polymer

A low-operating voltage and high performance polymeric field effect transistors using octadecylphosphonic acid-treated high-k AlOx and HfO₂ hybrid dielectrics were demonstrated. High-k metal oxide hybrid dielectrics were prepared by oxygen plasma treatment of deposited Al film for AlOx and by spin coating of solution-processable HfO₂ sol-gel solution for HfO₂ in combination with phosphoric acid-based self-assembled monolayer (SAM), resulting in high capacitance (10 nF/cm² for SiO₂, 600 nF/cm² for AlOx and 580 nF/cm² for HfO₂). With phosphoric acid-based SAM on high-k metal oxide and thermal annealing of thieno[3,2-b]thiophene-based conducting polymer, the device performance was significantly enhanced. The highest mobility of the transistors using ODPA-treated AlOx as a gate dielectric is 2.3 × 10^?2 cm² V^?1 s^?1 in the saturation region with the source-drain of ?2 V. In ODPA-treated HfO₂ hybrid dielectric, the saturated mobility is 1.1 × 10^?2 cm² V^?1 s^?1 and the threshold voltage was measured to be ?0.31 V, which is at least one order lower than SiO₂ hybrid dielectric (?3 V).     

Crystal Structure of a Non-Conductive Non-Stoichiometric Tetrathiafulvalenium Salt: (TTF)3(BF4)2

Abstract

(TTF)₃(BF₄)₂ crystallizes in the triclinic system, space group P1, a = 8.017(3), b = 8.601(1), c = 11.635(2) Å, α = 108.79(1), β = 100.96(2), γ = 99.09(2)°, Z = 1. The TTF entities are stacked in parallel columns arranged into parallel layers alternating with layers of BF₄ ^? anions. A TTF stack is constituted of (TTF⁺)₂ diads interspersed with TTF° monads; the TTF⁺-TTF⁺ overlap is of the ring-over-ring type while the TTF⁺-TTF⁺ overlap is of the bond-over-ring type. These features explain the low conductivity ([sgrave]_powdcr = 2 × 10^?5 Ω^?l cm^?1) of this apparently non-stoichiometric TTF salt.     

Study of the surface state density and potential in MIS diode Schottky using the surface photovoltage method

ABSTRACT

The effects of surface preparation and illumination on electric parameters of Au/GaN/GaAs Schottky diode were investigated. The thin GaN film is realized by nitridation of GaAs substrates with different thicknesses of GaN layers (0.7 – 2.2 nm). In order to study the electrical characteristics under illumination, we use an He-Ne laser of 632 nm wavelength. The I(V) current- voltage, the surface photovltage SPV measurement were plotted and analysed taking into consideration the influence of charge exchange between a continuum of the surface states and the semiconductor. The barrier height Ф_Bn, the serial resistance R_s and the ideality factor n are respectively equal to 0.66 eV, 1980 Ω, 2.75 under dark and to 0.65 eV, 1160 Ω, 2.74 under illumination for simple 1 (GaN theckness of 0.7 nm). The interface states density N_ss in the gap and the excess of concentration δn are determined by fitting the experimental curves of the surface photovltage SPV with the theoretical ones and are equal to 4.5×10¹² eV^?1 cm^?2, 5×10⁷ cm^?3, respectively, for sample 1 and 3.5×10¹² eV^?1 cm^?2, 7×10⁸ cm^?3 for sample 2 (GaN theckness of 2 nm). The results confirm that the surface photovoltage is an efficient method for optical and electrical characterizations.     

Semiconducting Properties of TI2Te3 Single Crystals

Electrical conductivity and Hall effect measurements were performed on single crystals of TI₂Te₃ to have the general semiconducting behaviour of this compound. The measurements were done at the temperature range 160–350 K. All crystals were found to be of p-type conductivity. The values of the Hall coefficient and the electrical conductivity at room temperature were 1.59 × 10³ cm³/coul and 3.2 × 10⁻² ω⁻¹ cm⁻¹, respectively. The hole concentration at the same temperature was driven as 39.31 × 10¹¹ cm⁻³. The energy gap was found to be 0.7 eV where the depth of impurity centers was 0.45 eV. The temperature dependence of the mobility is discussed.     

Influence of valence and coordination of manganese ions on spectral and dielectric features of Na2SO4–B2O3–P2O5 glasses

Sodiumsulpho borophosphate glasses with composition (40 ? x)Na₂SO₄–30B₂O₃–30P₂O₅: xMnO with x ranging from 0 to 5.0 mol% were manufactures. Dielectric spectra have been studied over a wide frequency range of 10²–10⁵ Hz and in the temperature range within 30–250 °C. The valance states of manganese ions and their ligand coordination in the glass network have been investigated using optical absorption, luminescence and ESR spectroscopy. The analysis of the these results has indicated that the manganese ions exist both in Mn²⁺ as well as in Mn³⁺ states and occupy prevailingly octahedral positions and serve as modifiers similarly to Na⁺ ions The values of dielectric parameters (dielectric constant, ε′(ω), loss tan δ and ac conductivity, σ_ac) were found to increase with increasing MnO content. They play a role of modifiers similarly to Na⁺ ions, create bonding defects and free ions viz., [SO₄]^2?, [POO_1/2O₂]^2?, [POO_0/2O₃]^3–, Na⁺ and (NaSO₄)^?. The migration of these charge carriers would build up space charge polarization and may be responsible for the enhanced dielectric parameters. The ac conductivity also is enhanced with increasing MnO content. The mechanism responsible for such increase is well explained based on the modifying action of Mn²⁺ ions.     

Synthesis,characterization and impedance spectroscopy of the new material [(CH3) (C6H5) 3P] 2CoBr4: a member of the A2BX4 family

The crystal structure of bis‐(methyltriphenylphosphonium) tetrabromocobaltate (II), [(C₁₉H₁₈P)₂ CoBr₄] is determined: M_r = 933.203, monoclinic, P2₁, a = 9. 6977 (3) Å, b = 12.5547 (4)Å, c = 16.4503 (6)Å, β = 105.603 (2)°, V = 1929.04 (11)ų, Z = 2, D_x = 1.607 Mg m^‐3, T = 298 K. Differential thermal analysis at high temperatures shows three endothermic peaks characterizing four phases, with onset temperatures at T₁= 313±2 K, T₂ = 320±4 K and T₃= 360±1 K. The structural instability detected via the temperature dependence of permittivity at T₁ is ascribed to order‐disorder transition associated with cation dipole reorientation. Permittivity and ac conductivity studies as a function of temperature (295 K‐375 K) and frequency (0.11 kHz < f <100 kHz) are presented. The results indicate the importance of the cation size and shape on the phase transitions in the system. Bulk conductivity behavior is thermally activated. The associated activation energies are in the range 2.9 to 1.0 eV depending on the temperature regime. Two contributions to the ac conductivity, one dominating at low temperatures and high frequencies which are characterized by superlinear frequency exponent and the second dominates at high temperatures characterized by a sublinear frequency exponent. The behavior is interpreted in terms of the jump relaxation model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)