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The effect of a lithium salt on the general polymer dynamics of poly(ethylene oxide) (PEO) and how these dynamical alterations affect the ionic conductivity and structural relaxations in (PEO)4:LiClO4 have been investigated. The study was based on differential scanning calorimetry (DSC) and dielectric relaxation studies. The DSC studies indicated an increased glass transition temperature of (PEO)4:LiClO4 as compared to that of PEO. The polymer-salt complex exhibited enhanced conductivity of σD.C. =3.2×10−7 S·cm−1 at room temperature (298K) due to the presence of mobile Li+ ions. Impedance data have been scaled and analyzed under conductivity and modulus formalisms over wide ranges of frequency and temperature for both PEO and (PEO)4:LiClO4. For PEO, the analysis of the scaled formalisms indicates that both the conductivity and the structural relaxation mechanisms are temperature-independent above the melting point of PEO. However, below the melting point, the nucleation and growth of spherulites and also the formation of ‘interphase’ regions in PEO result in a hindered long range D.C. conductivity, which, in turn, leads to a decoupling of the D.C. conductivity and the structural relaxation. However, for (PEO)4:LiClO4, by comparing the conductivity relaxation data with the calorimetric glass transition and analysis of scaled formalisms, a direct coupling between Li+ ion motions and polymer segmental dynamics is observed for the polymer electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: This review article presents a brief overview of synthesis and application aspects of fast fluoride ion conducting materials in the field of Solid State Ionics. Possible synthesis methodologies known in the literature for the preparation of various fluoride materials have been outlined. Further, their transport characteristics with respect to their crystal structure have been discussed. Various approaches influencing their ionic conductivity value in the light of synthesis methodology, composition, dopant concentration, crystallite size, microstructure etc. have been reviewed. At the end, possible technological applications of fast fluoride ion conducting materials in different solid state ionic devices have been presented. [Copyright &y& Elsevier]

Abstract: Thermal, structural and ionic conduction characteristics of lithium niobophosphate glass (mol% 50Li2O–45P2O5–5Nb2O5) are reported and compared with the characteristics of lithium metaphosphate glass (mol% 50Li2O–50P2O5). The presence of the second glass former (Nb2O5) not only improves the chemical durability and thermal stability but also enhances the conduction characteristics of lithium metaphosphate glass. The ionic conductivity measurements are reported in the extended temperature range i.e. above the glass transition temperature (Tg) where a non-Arrhenius temperature dependence of the ionic conductivity has been observed. The ion conduction process below Tg is governed by a well-defined activation energy whereas the conduction process above Tg is activated by at least two different phenomena discussed in the light of the structural relaxation and crystallization. [Copyright &y& Elsevier]

Abstract: (PEO)4:LiClO4 and the effect of δ-Al2O3 nano-fillers on the polymer electrolyte have been investigated by differential scanning calorimetry (DSC) and dielectric relaxation studies. The DSC studies indicated a decrease in the glass transition temperature of (PEO)4:LiClO4 in the presence of fillers. The polymer–salt complex exhibited a conductivity of σ D.C. =4.0×10−7 Scm−1 at room temperature (298K). In the presence of 4wt% δ-Al2O3 fillers, the ionic conductivity increased by almost two orders of magnitude and exhibited a value of σ D.C. =1.5×10−5 Scm−1 (298K). By comparing the conductivity data with the calorimetric glass transition it is evident that the enhanced conductivity can be attributed to a speeding up of the segmental polymer dynamics. Hence, the combined data indicate a direct coupling between Li+ ion motions and polymer segmental dynamics, even when 4wt% nano-fillers have been introduced. From the temperature dependence of the conductivity relaxation time, which, thus, is coupled to the structural (α) relaxation time, it is understood that the fragility of the polymer electrolytes decreases with increasing filler concentration. The decrease in T g and fragility suggests that the interaction between the nano-fillers and polymer is mainly non-attractive in nature. Moreover, the dielectric relaxation studies show that the β-relaxation speeds up with increasing concentration of filler particles. However, this speeding up is probably of less importance for the ionic conductivity. It was also found that the activation energy of the β-relaxation of PEO decreases in the presence of δ-Al2O3 nano-fillers and lithium salt. The strength of the β-relaxation increases also in the presence of salt ions. The γ-relaxation seems to be unaffected by the salt and fillers. [Copyright &y& Elsevier]

Abstract: The ionic conductivity of Sn(1−x)K x F(2−x) systems has been investigated as a function of composition and temperature using complex impedance spectroscopy. These materials have been prepared by normal solid state reaction method and characterized through XRD and DSC. The highest conducting sample has been prepared through mechanochemical synthesis technique in addition to solid state reaction method. The universal scaling behavior of the real and imaginary part of the impedance including complex impedance plots indicating temperature independent relaxation behavior has been demonstrated. This result is further supported by the scaling behavior of the real part of the conductivity. [Copyright &y& Elsevier]

Abstract: Crystallization kinetic studies of Li+ ion conducting mol% 60Li2O–40P2O5 glass indicate a 2-dimensional crystal growth mechanism as compared to the 3-dimensional growth mechanism for LiPO3 glass (mol% 50Li2O–50P2O5). Spectroscopic studies reveal that the structures of these two glass compositions differ considerably resulting in different mechanisms for crystal growth. Isothermal ionic conductivity studies further support 2-dimensional crystallization in mol% 60Li2O–40P2O5 glass. Above the glass transition temperature the ionic conductivity deviates from the usual Arrhenian temperature dependence due to the additional effect of the movement of the phosphate polymeric chains in the glass network. The ionic conductivity of the glass ceramic corresponding to the mol% 60Li2O–40P2O5 glass behaves in an Arrhenian fashion with an activation energy of 1.21eV, much higher than that of 0.77eV for the glass. Further, it is established using canonical scaling that the mechanism for ionic conduction is temperature independent. [Copyright &y& Elsevier]

Abstract: Conduction characteristics of the poly(ethylene oxide) based new polymer electrolyte (PEO)6:NaPO3, plasticized with poly(ethylene glycol) are investigated. Free standing flexible electrolyte films of composition (PEO)6:NaPO3 + x wt.%PEG400 (30⩽ x ⩽70) are prepared by solution casting method. A combination of X-ray diffraction (XRD), optical microscopy and differential scanning calorimetry (DSC) studies have indicated enhancement in the amorphous phase of polymer due to the addition of plasticizer. Further, a reduction in the glass transition temperature observed from the DSC result has inferred increase in the flexibility of the polymer chains. The cationic transport number of 0.42 determined through combined ac–dc technique has confirmed ionic nature of conducting species. Ionic conductivity studies are carried out as a function of composition and temperature using complex impedance spectroscopy. The electrolyte with maximum PEG400 content has exhibited an enhancement in the conductivity of about two orders of magnitude compared to the host polymer electrolyte. The complex impedance data is analyzed in conductivity, permittivity and electric modulus formalism in order to throw light on transport mechanism. A solid state electrochemical cell based on the above polymer electrolyte with a configuration Na|SPE|(I2 +acetylene black+PEO) has exhibited an open circuit voltage of 2.94V. The discharge characteristics are found to be satisfactory as a laboratory cell. [Copyright &y& Elsevier]