Loss Tangent Spectra Research Articles

Dielectric analysis of surface modified nano-graphite: effects of frequency and thickness

The nano-graphite (NG) and acid modified nano-graphite (ANG) have been synthesized from graphite powder via mixture of strong acid (sulphuric acid and nitric acid) respectively by a soft chemistry route involving microwave, ultrasonic method and characterized by high-resolution electron microscopy (HR-TEM), scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), clearly demonstrated the successful synthesis of acid modified NG. SEM images confirmed the surface morphology of NG, and ANG and HR-TEM study shows the nanoparticles size of NG and ANG. FTIR data confirmed the presence of acid functional groups on the surface of synthesized NG powder. XRD data of NG and ANG shows that 2θ is at 26.43° and 0.336 nm is an interlayer distance (d). NG and ANG pellets have been prepared for their dielectric analysis with frequency for different thickness. The dielectric loss tangent (tanδ) spectra show relaxation peak with frequency and peak shifts due to presence of polar groups in the ANG. The capacitance values of NG and ANG decrease with frequency and increase with thicknesses due to the capacitive nature of nanoparticles. The dielectric permittivity decreases with frequency and increases with thickness due to the charge orientation and dipole moment change of functional groups of synthesized NG, and ANG. The electrical conductivity of NG and ANG nanoparticles increases with frequency and thickness of NG and ANG pellets due to the conductive nature. Electrical conductivity and dielectric permittivity of NG and ANG are found to highly rely on thickness, according to the dielectric evaluation.

Green biopolymer and plasticizer for solid electrolyte preparation: FTIR, electrochemical properties and EDLC characteristics

In this study a green electrolyte was developed by incorporating methylcellulose (MC) polymer with potassium thiocyanate as ion provider and plasticized with glycerol to enhance salt dissociation. The purpose of glycerol addition was to improve DC conductivity and to enhance the performance of an electric double-layer capacitor (EDLC) device. The electrochemical and structural characteristics of the green electrolyte were examined. The broadening of the FTIR bands and a decrease in intensity indicated the interaction between the electrolyte components. The suitability of the electrolyte films for device applications was confirmed by measuring ionic conductivity using electrochemical impedance spectroscopy (EIS) skills. A significant amount of charge was concentrated at the electrode–electrolyte interface because of the high dielectric constant of the electrolyte. The loss tangent (tan δ) and modulus (M“) spectra obtained from electrical impedance spectroscopy showed distinct peaks associated with ion relaxation processes. The results of the transference number measurement (TNM) experiment indicated that ions were more influential than electrons. The stability of the film under different voltage conditions was evaluated using the linear sweep voltammetry (LSV) method. The performance of the EDLC was determined through cyclic voltammetry (CV) and charge–discharge evaluations. The CV pattern of the device at low scan rates showed a non-Faradaic mode of charge storage with a nearly rectangular shape. The newly constructed EDLC exhibited an initial capacitance per unit mass of 79F/g, a utilization efficiency of 87%, a power density of 1950 W/kg, and an energy storage density of 12.1 Wh/kg.

Formation of silver particles in [PVA:CS:PEG]-AgNO3 based biopolymer electrolyte membranes: Structural and electric transport properties study

[Chitosan (CS)-poly(vinyl) alcohol (PVA)-polyethylene glycol (PEG-200)]+xwt% silver nitrate (AgNO3) (x = 0, 10, 20, 30, 40) based biopolymer blend electrolytes (BPBEs) were prepared using solution casting method. FTIR results show the interaction of Ag+/NO3− with the constituents of polymers CS/PVA. XRD results reveal that the amorphousness increases with increasing AgNO3 concentration. Optical morphological (OM) images show that the silver, Ag(o) particles are agglomerated on the surface of the membrane. Temperature dependent dc conductivity (σdc) and dielectric relaxation frequency (fr) for BPBEs follow the Arrhenius type behavior and the sample containing 30 wt% salt has optimum dc conductivity, σdc∼1.7×10−4 S/cm at 30oC with lowest activation energy∼ 0.16 eV. The ac conductivity spectra follow the Jonscher's power law (JPL) with power law exponent, s > 1. The scaling of AC conductivity and loss tangent (tanδ) spectra were performed with respect to temperatures/concentrations of salt. The dielectric permittivity study reveals that the electrode polarization effect predominates at low frequencies. The Ionic Transference Number (ITN) measurement was used to determine the nature species of charge carrier, either ionic or electronic. The linear sweep voltammetry (LSV), result shows that 30% AgNO3containing sample has the electrochemical stability window (ESW) ∼+1.5 to -1.5 V.

Analyses of negative real permittivity behavior, AC conductivity and impedance properties of (YxEu1-x)Ba2Cu3O6.5 ceramics

In the present study, the dielectric, ac conductivity, and complex impedance properties of (YxEu1-x) Ba2Cu3O6.5 perovskite ceramics where x: 0; 0,4; 0,6; 1 have been examined from room temperature to 523 K between 1 Hz and 20 MHz frequency range. The ceramics have been synthesized by solid-state reaction method. The XRD analyses of the samples pointed out that they crystallize in an orthorhombic structure. While the highest orthorombicity factor has been observed for YBa2Cu3O6.5 ceramic, the reduced orthorhombicity in the other ceramics has been associated with the Eu substitution. On the other hand, the dielectric analyses of the samples have revealed a negative real permittivity (NRP) property of all ceramics regardless of the Eu substitution ratio and temperature. The origin of the NRP phenomenon has been explained based on the Drude model. However, it has been reported that the frequency interval at which the NRP is valid is maximum for x≥0.6 at high temperatures (T > 500 K). Additionally, both impedance and loss tangent spectra of the samples have been evaluated by establishing a correlation between NRP and the inductive character of the ceramics. The dc conductivity and the real component of complex impedance analyses imply the semiconducting nature and the negative thermal coefficient (NTC) of resistance of the ceramics. Ac conductivity analyses also indicate a pre-dominant CBH charge transport mechanism in the ceramics except for EuBa2Cu3O6.5.

Morphological, structural, optical, broadband frequency range dielectric and electrical properties of PVDF/PMMA/BaTiO3 nanocomposites for futuristic microelectronic and optoelectronic technologies

Polymer blend nanocomposite (PBNC) films consisted of fluoropolymer poly(vinylidene fluoride) (PVDF) and plexiglass polymer poly(methyl methacrylate) (PMMA) blend host matrix (fixed composition blend of PVDF/PMMA = 80/20 wt/wt%) with barium titanate (BaTiO3) ceramic nanofiller of varying concentrations (x = 0, 2.5, 5, 10, and 15 wt%) were prepared via a state-of-the-art solution-cast method. Scanning electron microscope (SEM) images evidenced high homogeneity of these PBNC films and a huge alteration in the spherulite morphology of the PVDF with the increase in dispersed BaTiO3 concentration in the polymer blend matrix. The X-ray diffraction (XRD) patterns identified the presence of electro-active polar β- and γ-phases of the PVDF crystallites in all the composite materials which are supported by the results of Fourier transform infrared (FTIR) spectra. The differential scanning calorimeter (DSC) thermograms explained the high melting temperature of these overlapped PVDF polymorphs and the degree of crystallinity altered anomalously with the variation of nanofiller concentration. The absorbance of ultraviolet-visible (UV-Vis) radiations enhanced while the direct energy band gap of the 80PVDF/20PMMA blend matrix and also the semiconducting BaTiO3 was found to decrease with the increased concentration of nanomaterial in the host polymer matrix. The ambient temperature broadband dielectric spectra covering the frequency range from 20 Hz to 1 GHz explain that the real part of complex dielectric permittivity reduced with a huge dispersion at higher radio frequencies where the dielectric loss tangent and electric modulus spectra exhibited an intense chain segmental relaxation process. The electrical conductivity of these PBNC films increased with frequency augmented and illustrated a small variation for different concentration composites. The experimental results demonstrated that these PVDF/PMMA/BaTiO3 films could be potential candidates for frequency tunable nanodielectric, electromagnetic interference shielders, a flexible dielectric substrate, thermal insulators, and bandgap regulated materials for futuristic microelectronic, capacitive energy storage, and optoelectronic technologies.

Enhancement of electrical and electrochemical properties of sodium bromide incorporated with poly (ethylene oxide)/poly (vinylidene fluoride-hexafluoropropylene) solid blend polymer electrolytes for electrochemical double layer capacitors

Sodium-ion conducting solid blend polymer electrolytes are prepared with Poly (ethylene oxide) (PEO)/Poly (vinylidene fluoride-hexafluoropropylene) P(VdF-HFP)/Sodium Bromide (NaBr) by solution casting technique. Different analysis such as structural, vibrational, electrical and electrochemical studies reveal promising properties of the prepared solid polymer electrolytes (SPE). The XRD analysis illustrates the increase in amorphous nature of the sample up to 8 wt% NaBr salt concentration. The complexation between polymers and salt has been examined by FTIR analysis. To examine the electrical conductivity, AC impedance analysis was performed in the temperature range of 303–373 K. The higher ionic conductivity (σ) of 1.10 × 10−3 S cm−1 was found for the solid polymer electrolyte (SPE) containing 8 wt% NaBr at room temperature. The temperature dependence of ionic conductivity resembles Arrhenius behavior. The dielectric behavior has been analyzed using dielectric permittivity (ε*) and the relaxation frequency (τ) has been calculated from the loss tangent spectra (tan δ). The modulus spectra indicate the non-Debye nature of the material. Wagner's DC polarization technique was used to compute the transference number. According to the LSV analysis, the solid blend polymer electrolytes have the suitable electrochemical potential window to be used in electrochemical devices. The cyclic voltammetry (CV) and charge-discharge studies (GCD) of the assembled electrochemical double-layer capacitor (EDLC) show specific capacitance (Csp) values of 12.9 F/g and 10.4 F/g respectively. Further the better performance of EDLC is confirmed with its energy density (3.25 to 2.12 Wh/kg), power density (750 to 2623 W/kg) as well as coulombic efficiency (98.2 %) after 1500 cycles.

Theoretical Studies of Nonlinear Relaxation Electrophysical Phenomena in Dielectrics with Ionic–Molecular Chemical Bonds in a Wide Range of Fields and Temperatures

This paper is devoted to the development of generalized (for a wide range of fields (100 kV/m–1000 MV/m) and temperatures (0–1500 K) in the radio frequency range (1 kHz–500 MHz)) methods for the theoretical investigation of the physical mechanism of nonlinear kinetic phenomena during the establishment of the relaxation polarization, due to the diffusion motion of the main charge carriers in dielectrics with ionic–molecular chemical bonds (hydrogen-bonded crystals (HBC), including layered silicates, crystalline hydrates and corundum–zirconium ceramics (CZC), etc.) in an electric field. The influence of the nonlinearities equations of the initial phenomenological model of dielectric relaxation (in HBC-proton relaxation) on the mechanism for the formation of volume–charge polarization in solid dielectrics is analyzed. The solutions for the nonlinear kinetic Fokker–Planck equation, together with the Poisson equation, for the model of blocked electrodes are built in an infinite approximation (including all orders k of smallness without dimensional parameters) of perturbation theory for an arbitrary order r of the frequency harmonic of an alternating external polarizing field. It has been established that the polarization nonlinearities in ion-molecular dielectrics, already detected at the fundamental frequency, are interpreted in the mathematical model (for the first time in this work) as interactions of the relaxation modes of the volume charge density calculated on different orders of spatial Fourier harmonics. At the fundamental frequency of the field, an analytical generalized expression is written for complex dielectric permittivity (CDP), which is expressed analytically in terms of special relaxation parameters, which are quite complex real functions in the fields of frequency and temperature. The theoretical CDP and the dielectric loss tangent spectra studied depend on the nature of the relaxation processes in the selected temperature range (Maxwell and diffusion relaxation; thermally activated and tunneling relaxation), which is relevant from the point of view of choosing exact calculation formulas when analyzing the optimal operating modes of functional elements (based on dielectrics and their composites) for circuits of instrumentation, radio engineering and power equipment in real industrial production.

Effect of Applied Electrical Stimuli to Interdigitated Electrode Sensors While Detecting 17α-Ethinylestradiol in Water Samples

The effect of impedance measurements of applied voltage on the detection of 17α-ethinylestradiol (EE2) in water samples using interdigitated electrodes (IDE) coated or not with thin films, is described. Firstly, the effect of immersion in EE2 aqueous solutions of layer-by-layer films prepared with poly(allylamine hydrochloride) (PAH), graphene oxide (GO), poly(1-(4-(3-carboxy-4-hydroxyphenylazo) benzene sulfonamido) 1,2 ethanediyl, sodium salt) (PAZO), polyethylenimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS) was analyzed. These results demonstrated that PAH/GO films desorb during the immersion on EE2 solutions, while EE2 adsorbs on PAH/PAZO and PEI/PSS films with characteristic time values of 16.7 and 7.1 min, respectively, demonstrating that both films are adequate for the development of EE2 sensors. However, as the adsorption characteristic time is shorter, and the EE2 adsorbed amount is smaller, the PEI/PSS films are more suitable for the development of sensors. The effect of the applied voltage was analyzed using both IDEs covered with PEI/PSS films as well as those uncoated. The capacitance spectra are best fitted to analyze this effect, and the loss tangent spectra are advantageous to analyze the aqueous media. Furthermore, it was concluded that lower voltage values are best suited to perform measurements of this nature, given that higher voltages lead to less reliable results and cause irreparable damage to the sensors.

Broadband Radio Frequency Dielectric Permittivity and Electrical Conductivity of Dispersed Tin Oxide and Silica Nanoparticles in Poly(Ethylene Oxide)/Poly(Methyl Methacrylate) Blend Matrix-Based Nanocomposites for Nanodielectric Applications

In regards to the advances in hybrid polymer nanocomposite (HPNC) materials for high-frequency nanodielectric applications, herein we report the broadband radio frequency range (1 MHz to 1 GHz) dielectric permittivity and electrical conductivity of composites of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blend matrices and oxide nanofillers (tin oxide (SnO2) and silica (SiO2)), in the form of PEO/PMMA/SnO2 and PEO/PMMA/SiO2 films at ambient temperature. The results confirmed that these HPNCs have low dielectric permittivity values which decrease slightly, from 3.4 to 2.8, with increasing nanofillers concentrations and the applied electric field frequency. The dependency of the dielectric permittivity on the different oxide nanoparticles sizes and their dielectric constant was explored. The dielectric loss tangent spectra of these hybrid materials indicated that they were reasonably low loss nanodielectrics having a dipolar orientation relaxation in the higher frequency region. The radiofrequency electrical conductivity of the HPNCs was found to increase linearly from ∼10−8 to 10−4 S/cm with the increase of frequency, and it was less dependent on the fillers concentrations. Considering the dielectric and electrical properties, it is proposed that these PEO/PMMA/SnO2 and PEO/PMMA/SiO2 composites could be highly useful materials for dielectric substrates and insulators in the development of radiofrequency operative flexible-type electrical and electronic components and devices.

Effect of ionic liquid on structural, thermal and electrical transport properties of PVA-PVP based polymer blend electrolyte membrane

The present paper deals with the loading effect of ionic liquid (IL), 1-ethyl-3-methylimidazolium methylsulfate [EMIM][MS] on structural and electrical transport properties of polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG)- salt, sodium methyl sulfate (MeSO4Na) based polymer blend electrolyte (PBE) films. The samples were prepared using conventional solution cast method. The x-ray Diffraction (XRD) result shows that PBE films has characteristic peak with broad halo appeared in the range 2θ = 19.95° to 22.72° reveals the amorphous nature (semi-crystalline).The % degree of crystalinity (X c ) of prepared IL based PBE films were found to decreases with increasing IL content. Fourier transform infrared (FTIR) in total attenuated reflectance (ATR) mode analysis reveals the interaction between the functional groups (C=O and O–H) of polymer electrolyte with the cation, EMIM+/anion of IL/salt. Thermogravimetric analysis (TGA) shows that IL based PBE samples decomposes in multistep and Td,onset/peak value decreases with IL loading. Sample containing 30 wt%IL shows optimum dc conductivity value ∼1.5 × 10−4 S cm−1 at 30 °C with minimum activation energy ∼0.21 eV. Logσ versus 1000/T plot for all PBE sample follow the Arrhenius type thermally activated process and activation energy decreased with increasing IL content in PBE films. Frequency dependent conductivity behavior for IL based PBE film follow the Jonscher’s power law with power law exponent, n value<1 (amorphous polymeric system). AC conductivity spectra and loss tangent spectra (tanδ) with respect to IL/temperature content scalled successfully. Dielectric relaxation behavior and conductivity relaxation were analyses with respect to IL content and temperature. Mobility, total number of charge/ion density, ion diffusivity was estimated. Ionic transference number (ITN) measurement (tion ∼0.98, tele ∼0.02) reveals that ions are principal charge carriers in present system. Linear sweep voltametry (LSV) and cyclic voltamerty (CV) measurements show that 30 wt%IL containing sample has electrochemical stability window (ESW) ∼±2.7volt and Faradic oxidation reduction peaks were observed, respectively.

Basics of teaching electrochemical impedance spectroscopy of electrolytes for ion-rechargeable batteries – part 2: dielectric response of (non-) polymer electrolytes

Abstract In the Part 2 of this article, we present the phenomenological response of the dielectric relaxation for polymer electrolytes monitored by electrochemical impedance spectroscopy (EIS) in terms of electrochemical point of view, such as impedance (Z*), permittivity (ε*), loss tangent (tan δ), modulus (M*) and conductivity (σ*) spectra. It is noteworthy to note that all the electrochemical aspects mentioned are of interest for conduction and seen as closely related to each other indirectly or directly. Two different systems; solid polymer electrolyte (SPE) [poly(ethylene oxide) (PEO) + lithium perchlorate (LiClO4)] and non-SPE [poly(methyl acrylate) (PMA) + LiClO4] were employed for discussion. EIS is a powerful technique to characterize the electrical properties of polymer electrolytes. The results suggest that impedance and modulus are of interest for decoupling of dielectric and electric properties by evaluating the short-range and long-range mobility of the charged entities, respectively. One is able to identify the conduction mechanism of the polymer electrolytes easily if the responses are well understood. The objective of this article to introduce a simplified yet an insightful background and technique that is easy to be followed and useful for educational purposes especially for beginners or young researchers for both undergraduates and postgraduates.

Detecting Traces of 17α-Ethinylestradiol in Complex Water Matrices

Hormones have a harmful impact on the environment and their detection in water bodies is an urgent matter. In this work, we present and analyze a sensor device able to detect traces of the synthetic hormone 17α-ethinylestradiol (EE2) below 10−9 M in media of different complexities, namely, ultrapure, mineral and tap waters. This device consists of solid supports with interdigitated electrodes without and with a polyethylenimine (PEI) and poly (sodium 4-styrenesulfonate) (PSS) layer-by-layer film deposited on it. Device response was evaluated through capacitance, loss tangent and electric modulus spectra and the data were analyzed by principal component analysis method. While the three types of spectra were demonstrated to be able to clearly discriminate the different media, loss tangent spectra allow for the detection of EE2 concentration, with a sensitivity of −0.072 ± 0.009 and −0.44 ± 0.03 per decade of concentration, for mineral and tap water, respectively. Detection limits values were found to be lower than the ones present in the literature and presenting values of 8.6 fM (2.6 pg/L) and of 7.5 fM (22.2 pg/L) for tap and mineral waters, respectively. Moreover, the obtained response values follow the same behavior with EE2 concentration in any medium, meaning that loss tangent spectra allow the quantification of EE2 concentration in aqueous complex matrices.

Sodium Ion-Conducting Polyvinylpyrrolidone (PVP)/Polyvinyl Alcohol (PVA) Blend Electrolyte Films

We report the synthesis of sodium ion-conducting polymer-blend electrolyte (NIPBE) thin films prepared by a standard solution-casting technique based on polyvinylpyrrolidone (PVP)/polyvinyl alcohol (PVA) and sodium bicarbonate (NaHCO3). The as-synthesized NIPBE thin films were flexible, free-standing and displayed good mechanical stability. The prepared films were characterized using various experimental techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), AC impedance spectroscopy, linear sweep voltammetry (LSV), cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR) and UV–visible spectroscopy. The SEM, XRD and DSC studies revealed a reduction in the crystallinity of the polymer-blend electrolyte with an increase in the content of NaHCO3 due to the plasticization effect of Na-salts. The FTIR spectra show the complexation behavior of our as-prepared NIPBEs. The optical properties (i.e., direct and indirect optical energy bandgaps, optical absorption edge) were estimated using UV–visible spectroscopy studies. The dynamic ion behavior of all the as-prepared samples was assessed by the frequency-dependent AC conductivity of the NIPBEs. Also, the dielectric constant and dielectric loss (e′ and e″), and electric modulus (M′ and M″) vs. frequency plots at different concentrations and at room temperatures, were reported. The relaxation frequency (τs) of the NIPBE films was determined from the loss tangent spectra (tanδ). The ionic conductivity of NIPBE films was found to increase with sodium salt concentration, with maximum conductivity of the order of ∼10−5 S/cm at 30 °C. CV measurements showed good electrochemical stability of the sample containing a high concentration of Na salts. The optimized NIPBEs showed ionic conductivity and electrochemical voltage stability which is good for application in energy storage devices.

Dielectric investigations on carbon nanotubes doped polymer dispersed liquid crystal films

We obtained carbon nanotubes (CNTs) doped polymer dispersed liquid crystal (PDLC) films using the nematic E7 and polymethyl methacrylate, a composite that combines the benefic characteristic of the liquid crystals (LC) and carbon nanoparticles. The clearing temperatures recorded by differential scanning calorimetry for the PDLC blends were found to be lower than the value recorded for pure E7 LC mixture with no significant impact of the CNTs’ concentration. Broadband dielectric spectroscopy (DS) measurements were performed in the $$ (10^{ - 1} \div 10^{7} )\;{\text{Hz}} $$ frequency range, in the temperature domain (280–350) K. From the DS study, a two order magnitude variation of the conductivity over the entire temperature range was observed. The presence of CNTs results in an increase of electrical conductivity, with increasing concentration. Because the loss tangent spectra have complex shapes, they were fitted using the generalized Havriliak–Negami functions, and the characteristic relaxation times were extracted. The dependency of the characteristic relaxation time on temperature was modeled using the Vogel–Fulcher–Tammann function, and it showed a temperature variation according to the Arrhenius law. The increase of the CNT concentration increases the activation energy of the molecular electric dipoles of the LC. The interface LC-polymer interactions influence the nematic to isotropic phase transition of the LC.

X-Band Microwave Absorption in Nd³⁺-Substituted Mg–Cd Spinel Ferrites Synthesized Under Microwave Sintering

The electromagnetic parameters and microwave-absorbing properties of Nd3+-substituted Mg–Cd spinel ferrites with the chemical formula Mg x Cd1– x Nd0.03Fe1.97O4 (where $x = 0$ , 0.2, 0.4, 0.6, 0.8, and 1.0) were investigated using vector network analyzer (VNA) in conjunction with the material measurement software. The permittivity of all the ferrites follows the usual dispersion behavior in the microwave frequency range. The behavior of ac conductivity and dielectric losses with frequency for various Mg content is quite similar. The variations in permeability with frequency for compositions with $x = 0.4$ , 0.6, and 1 in the frequency range of 10–12.4 GHz obeys Snoek’s law. The peaks observed in the magnetic loss tangent spectra may be due to spin rotation created in the ferrites. With an increase in magnesium content, the reflection loss peak gets deepened, signifying the increased improvement in the absorption properties. Thus, it can be stated that Mg-substituted Cd–Nd ferrites have better performance when compared with pure Cd–Nd ferrite, proposing it to be a suitable material for electromagnetic shielding applications in the $X$ -band.

Predominantly chain segmental relaxation dependent ionic conductivity of multiphase semicrystalline PVDF/PEO/LiClO4 solid polymer electrolytes

The solid polymer electrolyte (SPE) films comprise poly(vinylidene fluoride) (PVDF)/poly(ethylene oxide) (PEO) blend (75/25 wt/wt%) as host polymer matrix with lithium perchlorate (LiClO4) as ionic dopant for different salt concentrations (i.e., 5, 10, 15, 20, 25, and 30 wt%), and also varying compositional weight ratio PVDF/PEO blends (i.e., 75/25, 50/50, 25/75, and 10/90 wt/wt%) with 25 wt% concentration of LiClO4 were prepared by solution casting at 70 °C. The results obtained from X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy revealed that there is enormous alteration in the α- and β-phase crystals of the PVDF and the size and content of the PEO crystallites, and also the degree of crystallinity of these SPE materials with the variation of salt concentration and the polymer blend composition. Dielectric relaxation spectroscopy (DRS) was employed over the frequency range from 20 Hz to 1 MHz, at 27 °C for the study of the complex impedance, dielectric permittivity, dielectric loss tangent, ac electrical conductivity, and electric modulus spectra of the SPE films. All these spectra were analyzed separately and simultaneously by a novel ‘master curve representation’ procedure to unveil the contribution of various dielectric polarization processes (i.e., electrode, interfacial, molecular (dipolar), and the ionic) and their relaxations which are exhibited with increasing order of frequency and have substantial overlapping with the adjacent processes in these heterogeneous ion conducting materials. The loss tangent spectra of these materials manifest prominent dielectric relaxation peaks which attribute to the cation coordinated polymer chain segmental dynamics. The high frequencies ac electrical conductivity data of all these materials obey the power law, whereas the Nyquist plots of impedance data exhibit reasonably distinguishable bulk and electrode polarization frequency regions for the electrolytes having salt concentration ≥20 wt%. The inverse correlation observed between the relaxation time and the dc ionic conductivity establishes that the transportation of ions is predominantly coupled to the polymer chain segmental motion which assists the hopping between favourable conduction sites in the ion-dipole complexes. The SPE films are comparatively stiffer and have a slightly higher degree of crystallinity when the salt concentration is ≤ 15 wt% and they exhibit distinct dielectric, dc ionic conductivity, and relaxation behaviour as compared to that of the softer and lower crystallinity films having salt concentration ≥20 wt%. These SPE films possess good electrochemical performance and close-to-unity total ion transference numbers. Among these two sets of the SPE films, the maximum dc ionic conductivity was noted 2.01 × 10−5 S/cm at 27 °C for the 75PVDF/25PEO–30 wt% LiClO4 film from the set of different salt concentrations, and 5.61 × 10−6 S/cm for 25PVDF/75PEO–25 wt% LiClO4 film from the set of varying compositions of the polymer blend matrix. The considerable ionic conductivity values of these SPE films at ambient temperature and also their promising electrochemical performance corroborate them as novel ion conductors suitable for the development of solid-state rechargeable lithium-ion batteries.

Chitosan-PEG-NaI based bio-polymer electrolytes: structural, thermal and ion dynamics studies

BPE films based on [Chitosan (CS)-PEG]-NaI were prepared using solution cast technique. The prepared electrolyte films were subjected to thermal, structure and conductivity studies using TGA, XRD, ATR-FTIR and AC impedance spectroscopic techniques. The thermal gravimetric analysis (TGA) reveals that the CS and [CS-PEG]-NaI based films decomposes in multi step. Onset decomposition temperature (Td,onset) also decreases with increasing NaI content in CS-PEG based films. The [CS-PEG]-NaI based films are thermally stable upto ∼220.2 °C. XRD result shows that CS has semi-crystalline in nature having its characteristic peak appeared at 2θ ∼ 23.1°. The % degree of crystallinity (Xc) decreases with increasing NaI content in CS-PEG based films. ATR-FTIR study confirms the interaction between bio-polymer, CS with PEG and NaI. The sample containing 40 wt%NaI shows dc conductivity value ∼7.25 × 10−4 Scm−1at 30 °C. The values of frequency exponent s for BPE films were found to be 0.68 to 0.22. Scaling of ac conductivity with respect to NaI concentration has been performed. Mobility (μ) and total number density of charge carriers (N) were estimated from loss tangent spectra.

A Novel Two-Peak Analysis for Dielectric Spectroscopy

This paper describes a method for estimating model parameters $\varepsilon _{s}$ and $\Delta \varepsilon = \varepsilon _{s} - \varepsilon _{\infty }$ from the peaks in the imaginary permittivity and loss-tangent spectra. The analysis describes how measured parameters obtained from an impedance spectrometer, the magnitude of the impedance, and phase angle, are directly converted into complex permittivity and loss tangent. As an application, the method is used to detect and quantify the crystallization of skim-milk powder, which shows a dramatic change in the Debye parameters as it converts from the amorphous to crystalline state.

AC Conductivity and Dielectric spectra study of a blended solid polymer electrolyte.

Conductivity and dielectric spectra of a polymer blend electrolyte have been investigated in the temperature range ±20°C. AC conductivity data has been fitted with Jonscher's power law to confirm the hopping nature of ions. Further, the dielectric property has been studied by using the modulus and loss tangent spectra. Activation energy has been calculated from DC conductivity and loss tangent data. A similarity between the activation energy from DC conductivity and dielectric data indicates identical conducting species was involved in ion migration. Almond-West formalism has been applied to calculate the effective carrier concentration in the sample. Temperature variation of cation concentration shows a systematic decrease at sub-ambient temperature. A systematic change in DC conductivity, hopping frequency, and cation concentration at sub-ambient temperature indicates trapping of effective cation within the polymer matrix at sub-ambient temperature.

Conductive bio-polymer electrolyte iota-carrageenan with ammonium nitrate for application in electrochemical devices

Bio-polymer electrolyte iota-carrageenan (Ι-carrageenan) with ammonium nitrate (NH4NO3) has been prepared by solution-casting technique. The increase in amorphous nature of the bio-polymer electrolyte due to the addition of salt has been confirmed by X-ray diffraction analysis. From the XRD spectra, the average particle size has been calculated using the Debye–Scherrer formula and the value is 0.98 nm. The complex formation between the polymer and the salt has been confirmed by Fourier transform infra-red spectroscopy. The glass transition temperature of the bio-polymer Ι-carrageenan with NH4NO3 electrolytes has been found using differential scanning calorimetric technique. From the AC impedance spectroscopic analysis, the ionic conductivity value has been found to be 1.46×10−3S/cm at ambient temperature for the composition of 1.0g Ι-carrageenan: 0.4wt% NH4NO3. The temperature dependent conductivity of the polymer electrolyte obeys an Arrhenius relationship. The dielectric behavior has been analyzed using dielectric permittivity (ε*) and the relaxation frequency (τ) has been calculated from the loss tangent spectra (tan δ). The modulus spectra indicate non-Debye nature of the material. Ionic transference number has been found to be 0.95 for the polymer 1.0g Ι-carrageenan: 0.4wt% NH4NO3. The result reveals that the conducting species are predominantly due to ions. Electrochemical stability window of 2.46V has been measured by using linear sweep voltammetry for the highest ionic conducting membrane. A primary proton battery has been constructed with the highest conductivity sample and open circuit voltage has been found to be 1.04V. Fuel cell has been constructed with the highest proton conductivity polymer 1.0g Ι-carrageenan: 0.4wt% NH4NO3 and the open circuit voltage found to be 442mV.