Scaling Of Ac Conductivity Research Articles

Investigation of the relationship between morphology-electrical transport phenomena in iron-doped quaternary glass nanocomposite

The Fe doped nano nanocomposite glassy system xFe·(1-x)·(0.3 V2O5·0.2MoO3·0.4CdO·0.1ZnO) (x = 0.2, 0.3, and 0.4) has been studied by different techniques. Lattice strain (ɛ) increases with increasing iron (x) content in the glass system, which facilitates the enhancement of electrical phenomena such as transport using the polaron hopping mechanism. The AC conductivity spectra at different temperatures have been computed using Almond–West formalism and a modified correlated barrier hopping model. AC, as well as DC conductivity, have increased with increasing Fe content in compositions. The DC activation energies are found to be 0.53, 0.48, and 0.44 eV for the values of x = 0.2, 0.3, and 0.4 respectively. Both DC activation energy (Eσ) and activation energy (EH) for hopping frequency have decreased with Fe content. AC conductivity scaling data has explored that the common electrical relaxation mechanism is temperature-independent as well as composition-dependent.

Influence of Sb doping on thermal properties and electrical conductivity mechanism of SbxSe50–xSn20Te30 chalcogenide glassy systems

Tunability of thermal, and electrical characteristics of SbxSe50-xSn20Te30 (x = 2, 4, 6, and 8 at. %) bulk glass systems with varying doping concentrations are the major objective of this study. The melt quenching technique has been employed to synthesize the samples. Various thermal parameters have been inspected by using DSC measurements. The effect of Sb addition on the glass transition temperature (Tg), crystallization temperature (Tc), peak crystallization temperature (Tp), and melting temperature (Tm) have been observed from DSC thermograms. The dependence of Tg, Tc, Tp, and Tm on the heating rate has been measured. The thermal analysis is performed under non-isothermal conditions at heating rates of 5, 10, 15, and 20 K/min. The activation energies for the glass transition temperature are estimated by using the Kissinger method and are found to decrease from (211.21-168.85) KJ.mol−1. Thermal stability and glass forming ability for all glassy compositions have been examined in terms of Hruby's parameter. In addition, electrical conductivity mechanisms over vast temperature and frequency ranges are analyzed. The DC conductivity mechanism has been analyzed by deploying Mott and Greaves's variable range hopping model, while the AC conductivity mechanism has been analyzed by deploying the modified correlated barrier hopping model. AC conductivity scaling property has been examined by using the Pan and Ghosh model. The influence of Sb addition has been observed as the DC and AC conductivity increases with the increase of doping concentration.

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.

Mixed ionic and electronic conductivity in the quaternary V2O5–Na2O–ZnO–P2O5 glass system

The melt quenching method was adopted to synthesize glasses with the formula xV2O5–(0.4-x) Na2O–0.35ZnO–0.25P2O5 (x = 0.05, 0.1, 0.15, 0.2, and 0.25). X-ray diffraction patterns for the x = 0.05 sample showed the complete amorphous structure, whereas other composites revealed the development of nanocrystallites over the amorphous glassy networks. DSC measurement showed that glass transition temperature reduced as V2O5 concentration rose, and values were consistent with modified CBH model theoretical (fitting) data. DC conductivity for x = 0.05 and 0.1 composites followed an Arrhenius-type relation and linearity against the reciprocal of temperature, revealing ionic conductivity. On the contrary, the electronic or small polaron hopping mechanism was responsible for DC conductivity for all other composites. AC conductivity mechanism was described by the modified correlated barrier hopping model, and ideal glass transition temperatures were predicted (361 °C (x = 0.05) to 412 °C (x = 0.25)). It was observed that with rising V2O5 content (x), there was blockage of ionic pathways of Na+ ions, causing the ionic conductivity to decline and the electronic or small polaronic conductivity to enhance, as the radius of small polaron reduces. AC conductivity scaling property established that the time-temperature superposition principle and the BNN relation did not hold for the systems.

Structural modifications, optical response, and electrical conductivity mechanism of Bi2O3 doped in P2O5–V2O5–MoO3 nanocomposite glass systems

Structural, optical and electrical conductivity mechanism of four compositional series of xBi2O3-(1-x)(0.30P2O5–0.35V2O5–0.35MoO3) [x = 0.05, 0.15, 0.25, and 0.35] have been investigated. XRD pattern affirms the existence of nanocrystallites in the glassy network, which affects the structural, optical and electrical alterations. The structural variation leads to an increase in the density of all the glassy systems. The FTIR analysis reveals the shift of different band positions suggesting structural alterations. The electrical conductivity investigation reveals the decreasing values of ac and dc activation energy, which enhances the ac and dc conductivity. The validity of Mott's VRH model has been examined and the value of hopping energy has been estimated. The obtained DC conductivity spectra of all samples have been fitted with Greaves's model. The AC conductivity scaling model of Pan and Ghosh has been used to demonstrate the electrical conduction relaxation method. In the spectroscopic investigation, by deploying the Tauc's plot, the optical band gap energies of the studied glass compositions are estimated. The calculation of Urbach energy values allows us to estimate the disorders of glassy nanocomposites. Different spectroscopic parameters like refractive index, polarizability, reflection factor, and reflectivity have been studied.

Electrical conductivity and relaxation in lithium-doped barium vanadate glasses investigated by impedance spectroscopy

We present herein a detailed study of the electric and dielectric properties of glasses with the composition 60V2O5–(40–x)BaO–xLi2O, where x = 10, 15, 20, or 25 mol%. The conduction and relaxation mechanisms have been studied by impedance spectroscopy over the frequency range from 40 Hz to 10 MHz and at various temperatures. With constant transition metal oxide content, the conductivity variation in the glasses is assumed to be mainly due to an ionic contribution. The dependence of electrical conductivity on frequency has been analysed using Jonscher's power law. Properties of the glasses, such as electric modulus loss and relaxation mechanism, have been analysed in terms of electric modulus using the Kohlrausch–William–Watts (KWW) equation, which describes the relaxation behaviour of the mobile ions as non-Debye in nature. Scaling of ac conductivity and electric modulus data has shown that conductivity relaxation is independent of temperature. The non-monotonic variation in the stretching parameter β has been found to show a positive correlation with various activation energies, namely electrical activation energy, relaxation activation energy, and the activation energy from the Anderson–Stuart model. The anomalous behaviour of activation energy with respect to conductivity has been substantiated through structural insight. The conductivity was found to be highest in glasses with 25 mol% Li2O, while coupling between the mobile ions was best for glasses with 20 mol% Li2O.

Investigation of AC Conductivity Scaling and Dielectric Relaxation Dynamics of Chitosan/Iron Complexes

Complexes of chitosan-iron (Cs/Fe) were prepared electrochemically in acidic aqueous media in one compartment cells. The AC electrical conductivity of the Cs/Fe complexes was investigated in a wide range of frequency at various temperatures. The general behavior of the AC conductivity was found to be characterized by three different regions and, therefore, it was analyzed based on the universal power law to interpret the dispersive behavior of the conductivity. The activation energy (Ea ) of the conductivity was estimated and was found to be frequency dependent. The AC conductivity scaling of the complexes was investigated using various parameters. It was found that the conductivity spectra of all samples could be successfully collapsed into a master curve confirming that the relaxation mechanism was temperature independent under conductivity formalism in a certain range of temperature. The dielectric relaxation dynamics of the Cs/Fe complexes were investigated using the electric modulus. The behavior of the imaginary part of the electric modulus, M//(ω), of all samples showed asymmetric relaxation peaks with a red shift toward higher frequencies upon increasing the temperature. The Cole-Cole and scaling behavior of the real and imaginary parts of the electric modulus were investigated.

Dielectric relaxation and scaling of AC conductivity observed in mixed valence perovskite Eu2CoMnO6

Monophasic and polycrystalline double perovskite Eu2CoMnO6 has been synthesized, and its structural characterization, frequency and temperature-dependent dielectric relaxation have been studied. Observed thermally activated dielectric relaxation was explained using the empirical Havriliak–Negami (HN) dielectric relaxation function with an estimated activation energy [Formula: see text] [Formula: see text] 0.22 eV and attempt frequency [Formula: see text] [Formula: see text] 2.46 × 109 Hz. The frequency-dependent AC conductivity data, over a wide range of temperature (100–325 K), followed the empirical universal power law behavior ([Formula: see text], [Formula: see text] is the constant exponent) showing two different frequency exponents, respectively, in the high- and low-temperature regions. The high-temperature ([Formula: see text] 275 K) conductivity data followed the continuous time random walk (CTRW) approximation model proposed by Dyre. However, this model failed to reproduce the observed conductivity spectra in the low-temperature side ([Formula: see text] 200 K). Interestingly, both the high- and low-temperatures’ conductivity data can be scaled to the master curve with suitably chosen scaling parameters.

Understanding the sodium-ion dynamics in NASICON (Na3Al2P3O12) glass containing NaF: Scaling of electrical conductivity spectra

Quest for high ion-conducting solid electrolyte materials for sodium-ion batteries has been tremendously increasing. Glass materials are a potential solid electrolyte for high-energy Na-ion batteries. Nevertheless, the effective research on glass materials for their applications in Na-ion batteries is dawdling due to its low ionic DC-conductivity and poor understanding of the dynamics of mobile cations. Herein, we have attempted to address the effect of substitution of NaF for Al2O3 on the conductivity of Na3Al2P3O12(NAP) glass (mol%: 37.5P2O5–25.0Al2O3–37.5 Na2O). Raman spectra reveal that the increase in the substituent NaF concentration significantly affects the coordination of Al3+ and the distribution of sodium cations in the network structure of NAP glass. Impedance spectra reveal that the change in conductivity of NAP glass with an increase in the NaF concentration is highly dependent on a specific temperature range. At a lower temperature range, (<150 °C), the conductivity increases initially with the increase in NaF concentration and it decreases with any further increase in the NaF concentration; whereas, at temperatures above 150 °C, the conductivity increases continuously with an increase in the NaF concentration. The frequency-dependent AC-conductivity has been analyzed using the time-temperature scaling principle (TTSP) based on Summerfield and Ghosh scaling procedures to probe the ion conduction mechanism. The NAP glass that contains low NaF concentrations (<7.5 mol%) obeys the AC-conductivity scaling, i.e., it satisfies the TTSP principle, with respect to temperature based on the Summerfield scaling procedure; this indicates that the sodium-ion dynamics are independent of the temperature. The scaled AC-conductivity curves for NAP glass containing high NaF concentrations (>10 mol%) have deviated from Summerfield scaling and further indicate that the fraction of sodium-ions responsible for the ionic conductivity is decreasing with an increase in the temperature. Scaling of AC-conductivity curves for all the glass samples using the Ghosh procedure suggests that the number density along with the hopping distance of sodium ions changes with increasing temperature. The Modified random network structural model has been further utilized to explain the variation in the NAP glass conductivity with an increase in the NaF concentrations. The outcome of this work will certainly aid in designing the chemical compositions of glasses for the development of solid electrolyte materials for their applications in Na-ion batteries.

Proton dynamics in superprotonic Rb3H(SeO4)2 crystal by broadband dielectric spectroscopy

Broadband dielectric and AC conductivity spectra (1 Hz to 1 THz) of the superprotonic single crystal Rb3H(SeO4)2 (RHSe) along the c axis were studied in a wide temperature range 10 K < T < 475 K that covers the ferroelastic (T < 453 K) and superprotonic (T > 453 K) phases. A contribution of the interfacial electrode polarization layers was separated from the bulk electrical properties and the bulk DC conductivity was evaluated above room temperature. The phase transition to the superprotonic phase was shown to be connected with the steep but almost continuous increase in bulk DC conductivity, and with giant permittivity effects due to the enhanced bulk proton hopping and interfacial electrode polarization layers. The AC conductivity scaling analysis confirms validity of the first universality above room temperature. At low temperatures, although the conductivity was low, the frequency dependence of dielectric loss indicates no clear evidence of the nearly constant loss effect, so-called second universality. The bulk (intrinsic) dielectric properties, AC and DC conductivity of the RHSe crystal at frequencies up to 1 GHz are shown to be caused by the thermally activated proton hopping. The increase of the AC conductivity above 100 GHz could be assigned to the low-frequency wing of proton vibrational modes.

Fabrication and performances of high lithium-ion conducting solid electrolytes based on NASICON Li1.3Al0.3Ti1.7-xZrx(PO4)3 (0≤ x≤ 0.2)

Solid electrolytes are the key component in designing all-solid-state batteries. The Li1.3Al0.3Ti1.7(PO4)3 (LATP) structure and its derivatives obtained by doping various elements at Ti and Al site acts as good solid electrolytes. However, there is still scope for enhancing the ionic conductivity using simple precursors and preparation methods. In this study, the Li superionic conductors Li1.3Al0.3Ti1.7-xZrx(PO4)3 (LATZP) with 0 ≤ x ≤ 0.2 have been successfully prepared by the solid-state reaction route. The structural, morphological, and ionic transport properties were analyzed using several experimental techniques including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and impedance spectroscopy (IS). The presence of two relaxation processes corresponding to grain and grain boundary was studied using various formalisms. We have observed that grain effects dominate at lower temperatures (<100 °C) while the grain boundary at higher temperatures (> 200 °C) on ionic conductivity. The relaxation mechanisms of grain and grain boundaries were investigated by the Summerfield scaling of AC conductivity. The highest total ionic conductivity of 2.48 × 10-4 S/cm at 150 °C and 5.50 × 10-3 S/cm at 250 °C was obtained for x = 0.1 in Li1.3Al0.3Ti1.6Zr0.1(PO4)3 sintered at 950 °C/6 h in the air. The ionic conductivity value was found to be higher than the ionic conductivity reported for LATP prepared via solid-state reaction mechanism using the same precursors and conditions.

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.

Structural and ion transport properties of sodium ion conducting Na2MTeO6 (M= MgNi and MgZn) solid electrolytes

Solid-state electrolytes Na2MTeO6 (M = MgNi and MgZn) were prepared via a conventional solid-state reaction method. Structural properties of the samples were investigated by using powder X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS) techniques. XPS and XRD studies indicate the phase pure hexagonal layered P2-type structure of samples. Raman and FTIR spectroscopy reveal the possible bending and stretching vibration modes for Te–O and other metal oxides. The ion transport properties of the solid electrolytes were investigated by using AC impedance spectroscopy. The electrical properties were examined by means of classical brick layer model. The specific grain conductivity (σg) is found to be 2.13 × 10−5 S cm−1 and 0.90 × 10−5 S cm−1 at 20 °C for Na2MgNiTeO6 and Na2MgZnTeO6 electrolytes, respectively. The activation energy of σg for Na2MgNiTeO6 and Na2MgZnTeO6 is found to be 0.59 eV and 0.36 eV respectively for the temperature below 30 °C. Summerfield AC conductivity scaling analysis of samples is performed. These electrolytes could be potential candidates in solid-state Na+ battery applications.

Effect of IL incorporation on ionic transport in PVdF-HFP-based polymer electrolyte nanocomposite doped with NiBTC-metal-organic framework

Ni-based metal-organic framework (MOF), nickel 1,3,5-benzene tricarboxylate (NiBTC) has been synthesized by solvothermal method and incorporated with ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) at varying weight ratios to use as nanofiller in the polymer matrix of poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP). The structural properties of MOF-NiBTC-based composite polymer electrolyte system upon IL incorporation have been investigated by XRD, FTIR, BET, scanning EXAFS and XANES techniques. Shifting of vibrational modes of –COOH groups is observed from FTIR spectra due to strong interaction of Ni metal cluster with BF4− anion of the IL. Local coordination structure and oscillation periodicity of Ni K-edge are investigated in R-space and k-space from the EXAFS as well as XANES spectra. Asymmetric oscillatory behavior with reduction in coordination number is observed upon IL incorporation due to strong interaction of guest IL with the host MOF-NiBTC. Dielectric relaxation and scaling of AC conductivity have been analyzed in the temperature range of 300–380 K and frequency range of 42 Hz–5 MHz. Non Debye type dielectric relaxation dynamics is observed due to short range hopping of ions. Ion concentration and temperature independent scaling behaviors are followed by the composite polymer electrolyte membranes. Optimum ionic conductivity of 6.5 × 10−3 S cm−1 and electrochemical stability up to 5.7 V have been obtained at 50 wt% of IL incorporation in the porous nanocomposite electrolyte system.

Dielectric relaxation dynamics and AC conductivity scaling of metal-organic framework (MOF-5) based polymer electrolyte nanocomposites incorporated with ionic liquid

Dielectric relaxation dynamics and AC conductivity scaling of a metal-organic framework (MOF-5) based poly (vinylidene fluoride-co-hexafluoropropylene) (PVdf-HFP) incorporated with 1-Butyl-3-methylimidazolium hexafluorophosphate have been studied over a frequency range of 40 Hz–5 MHz and in the temperature range of 300 K–380 K. High values of dielectric permittivity () having strong dispersion are obtained at low frequency because of interfacial polarization. The real part of the dielectric modulus spectra (M′) shows no prominent peak, whereas the imaginary part (M″) shows certain peaks, with a reduction in relaxation time (τ) that can be attributed to a non-Debye relaxation mechanism. The spectra also depict both concentration- and temperature-independent scaling behavior. The power law dependent variation of AC conductivity follows the jump relaxation model and reveals activated ion hopping over diffusion barriers. The value of the frequency exponent is observed to decrease with increasing concentration of ionic liquid, indicating the forward hopping of ions in the relaxation process. The AC conductivity scaling curves at different temperatures also depict the temperature-independent relaxation dynamics.

Structural, thermal and dielectric properties of in-situ reduced graphene oxide − polypyrrole nanotubes nanocomposites

Reduced graphene oxide (RGO)-polypyrrole nanotubes (PPyNTs) nanocomposites have been synthesized by in-situ chemical reduction of graphene oxide using PPyNTs as spacers. Scanning electron microscopy displays homogeneous dispersion of 1D PPyNTs onto the 2D RGO nanosheets. Significant improvement in the crystallinity of the nanocomposites with increasing RGO concentration has been confirmed from X-ray diffraction results. The investigation of thermal stability in the range of 50–690°C reveals superior thermal stability of the nanocomposites compared to that of PPyNTs. Dielectric permittivity investigation exhibits enhancement in dielectric constant with RGO concentration due to interfacial polarization at the interfaces of RGO and PPyNTs. Relaxation of interfacial polarization at higher frequencies is established with a relaxation peak in the imaginary modulus formalism. The maximum ac conductivity of 1.45×10−4S/cm is achieved for 40wt.% of RGO. Scaling of ac conductivity suggests that the conductivity relaxation process is independent of filler concentration.

Swift heavy ion irradiation effects on structural, optical properties and ac conductivity of polypyrrole nanofibers

ABSTRACTPolypyrrole (PPy) nanofibers have been synthesized by interfacial polymerization method and irradiated with 160 MeV Ni12+ ions under vacuum with fluences in the range of 1010–1012 ions/cm2. High-resolution transmission electron microscopy results show that upon swift heavy ion (SHI) irradiation the PPy nanofibers become denser. The crystallinity of PPy nanofibers increases upon SHI irradiation, while their d-spacing decreases. Upon SHI irradiation, the polaron absorption band gets red-shifted indicating reduction in the optical band gap energy of the irradiated PPy nanofibers. The indirect optical band gap energy is decreased as compared to corresponding direct optical band gap energy. The number of carbon atoms per conjugation length (N) and carbon atoms per cluster (M) of the SHI-irradiated PPy nanofibers increase with increasing the irradiation fluence. Fourier transform infrared spectra reveal the enhancement in intensity of some characteristic vibration bands upon SHI irradiation. The thermal stability of the PPy nanofibers is enhanced on SHI irradiation. The charge carriers in both pristine and irradiated PPy nanofibers follow the correlated barrier hopping mechanism. Scaling of ac conductivity reveals that the conduction mechanism is independent of the SHI irradiation fluence.

Conductivity and modulus formulation in lithium modified bismuth zinc borate glasses

The conductivity and modulus formulation in lithium modified bismuth zinc borate glasses with compositions xLi2O–(50-x) Bi2O3–10ZnO–40B2O3 has been studied in the frequency range 0.1 Hz–1.5 × 105 Hz in the temperature range 573 K–693 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the studied compositions, the dc conductivity (σdc), crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of the experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating centre (Hf) and enthalpy of migration (Hm) have been estimated. It has been observed that number of charge carriers and ac conductivity in the lithium modified bismuth zinc borate glasses increases with increase in Li2O content. Further, the conduction mechanism in the glass sample with x = 0 may be due to overlapping large polaron tunneling, whereas, conduction mechanism in other studied glass samples more or less follows diffusion controlled relaxation model. The ac conductivity is scaled using σdc and ωH as the scaling parameter and is found that these are suitable scaling parameter for conductivity scaling. Non-Debye type relaxation is found prevalent in the studied glass system. Scaling of ac conductivity as well as electric modulus confirms the presence of different type of conduction mechanism in the glass samples with x = 0 and 5 from other studied samples. The activation energy of relaxation (ER) and dc conductivity (Edc) are almost equal, suggesting that polarons/ions have to overcome same barrier while relaxing and conducting.

Charge-carrier relaxation dynamics and ac conductivity scaling of poly(3,4-ethylenedioxythiophene) nanoparticles

An investigation of the dielectric characteristics of poly(3,4-ethylenedioxythiophene) nanoparticles has been conducted in the frequency range 20 Hz–2 MHz and the temperature range of 80–300 K through the studies of dielectric permittivity, modulus formalism and ac conductivity. High-resolution transmission electron micrographs confirm the formation of well-ordered spherical nanoparticles. Micro-Raman spectra confirm the conformational transition from benzenoid to quinoid structure with increasing dopant concentration. Linear variation of imaginary permittivity with frequency suggests that the dc conduction process is more significant than interfacial polarisation. The presence of single relaxation peak in the imaginary modulus formalism indicates the Debye-type relaxation. The decrease of frequency exponent with temperature confirms that the charge transport takes place through correlated barrier hopping mechanism. The scaling of ac conductivity spectra confirms that the relaxation dynamics of charge carriers in the poly(3,4-ethylenedioxythiophene) nanoparticles system is temperature independent.

Studies on structural, thermal and AC conductivity scaling of PEO-LiPF6 polymer electrolyte with added ionic liquid [BMIMPF6

Preparation and characterization of polymer electrolyte films of PEO+10wt.% LiPF6 + xwt.% BMIMPF6 (1-butyl-3-methylimidazolium hexafluorophosphate) containing dopant salt lithium hexafluorophosphate (LiPF6) and ionic liquid (BMIMPF6) having common anion PF6- are reported. The ionic conductivity of the polymer electrolyte films has been found to increase with increasing concentration of BMIMPF6 in PEO+10 wt.% LiPF6 due to the plasticization effect of ionic liquid. DSC and XRD results show that the crystallinity of polymer electrolyte decreases with BMIMPF6 concentration which, in turn, is responsible for the increase in ionic conductivity. FTIR spectroscopic study shows the complexation of salt and/or ionic liquid cations with the polymer backbone. Ion dynamics behavior of PEO+LiPF6 as well as PEO+LiPF6 + BMIMPF6 polymer electrolytes was studied by frequency dependent conductivity, σ(f) measurements. The values σ(f) at various temperatures have been analyzed in terms of Jonscher power law (JPL) and scaled with respect to frequency which shows universal power law characteristics at all temperatures.