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Ferroelectric ceramic–polymer composites consisting of Poly Vinyledine Fluoride–Hexa Fluoro Propylene (PVDF-HFP) as polymer host and 0.5Ba(Zr0.2Ti0.8)O3−0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) ceramics as filler were prepared using solution casting technique. These composites are characterized for structural, microstructural, vibrational, optical, dielectric and ferroelectric properties at various experimental conditions. The electroactive β phase fraction (observed from XRD and FTIR analysis) increases as the filler concentration increases up to 20 wt% of BZT-BCT and above that its value decreases. FTIR results were analyzed to understand the mechanism of enhancement of β phase by the interaction between negatively surface charged ions of filler with the CH2 dipole of polymer matrix. UV–visible spectroscopy also employed to confirm polymer–ceramic filler interaction. Variation of the dielectric constant with different filler concentrations is explained using the percolation theory. Finally, the interplay between the functional properties and the β phase is discussed in detail. [ABSTRACT FROM AUTHOR]

Conductivity relaxation using modulus formalism has been used to explore the coupling of ionic conductivity to dielectric relaxation in polymer electrolyte based on polyethylene oxide complexed with various content of LiAsF6. The temperature dependence of conductivity followed the VTF behavior suggesting close correlation between conductivity and the segmental relaxation process in polymer electrolytes. The coupling of conductivity to the segmental process has been discussed in terms of coupling index. For all compositions studied, the coupling index was within the range of 1-11 in the temperature range of investigation, which was in agreement with the coupled systems. [ABSTRACT FROM AUTHOR]

Abstract: The effect of plasticizer (polyethylene glycol, PEG200) on dielectric and electrical properties of an ionically conducting polymer nanocomposites PEO25-NaI+5wt.% DMMT (dodecyl amine modified Na+-montmorillonite)+ x wt.% PEG200 with different value of x has been investigated. At low frequency, the variation of relative dielectric constant with frequency shows the presence of material electrode interface polarization processes. The tangent loss peaks appearing at a characteristic frequency suggest the presence of relaxing dipoles in all the samples. On addition of plasticizer, the peak shifts towards higher frequency side suggesting the speed up the relaxation time. The electrical modulus formalism is used to study the ionic relaxation processes in these composites in terms of conductivity relaxation time. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled. The frequency dependence of ac conductivity follows the universal power law with a small deviation in the low frequency region due to the electrode polarization effect. [Copyright &y& Elsevier]

Abstract: A nanocomposite electrolyte comprising a polymer–salt complex (PEO25–NaClO4) and an organically modified sodium montmorillonite (Na-MMT) has been prepared using tape casting technique. The effect of clay concentration on structural, microstructural and electrical properties has been investigated. X-ray diffraction (XRD) analysis confirmed the formation and structure of the nanocomposite. FTIR analysis suggested a clear evidence of polymer–ion–clay interaction indicated by the changes appearing in the ν(ClO4 −) and ν(C–O–C) bands as a function of the clay concentration. The surface properties and microstructure has been studied using atomic force microscopy (AFM) technique. Complex impedance spectrum (CIS) shows the existence of bulk and grain boundary effects in the nanocomposite films. The temperature dependence of electrical conductivity obeys VTF pattern of variation. [Copyright &y& Elsevier]

A new plasticized composite polymer electrolyte (PCPE) based on poly(ethylene oxide)–NaClO4 dispersed with a ceramic filler (SnO2) and plasticized with polyethylene glycol (PEG200) is reported. The effect of plasticizer concentration on changes in structure/microstructure and their correlation with physical properties has been investigated and reported. A substantial enhancement in the electrical conductivity, by two orders of magnitude at room temperature, of the PCPE has been noticed when compared with that of composite polymer electrolyte (CPE) films without any plasticizer. This enhancement in electrical conductivity of the PCPE films agrees well with the changes in the local microstructure/structure on plasticizer addition. Grain boundary resistance (Rgb) and glass transition temperature (Tg) have been observed to decrease with increasing concentration of PEG200. Plasticizer addition has resulted in the suppression of crystallinity as observed from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The DSC results indicate enhancement in the volume fraction of the amorphous phase, which appears to be consistent with the broadening in the polymer host peaks observed in X-ray diffractograms. The improvement in electrical conductivity has been achieved without any sharp deterioration in the thermal, electrochemical or mechanical stability of the PCPE thin films. These observations have been interpreted in terms of the action of plasticizer as a diluent/co-solvent. [Copyright &y& Elsevier]

We report the mechanism to enhance the dielectric and ferroelectric behavior of polymer-ceramic composites through surface hydroxylation of 0.5Ba(Zr 0.2 Ti 0.8)O 3 -0.5(Ba 0.7 Ca 0.3)TiO 3 (BZT-BCT) ceramic filler-particles embedded in PVDF-HFP copolymer matrix. Varying the hydroxylated h-(BZT-BCT) filler particle-content (φ = 0–40 wt%) in PVDF-HFP copolymer matrix, composite films (of ~75 μm thickness) were prepared. We observed that, with an increase in filler content up to an optimum concentration of 15 wt% , a microstructure with gradually denser particle-arrangement and enhanced particles-polymer surface interaction is exhibited, which leads to improved dielectric and ferroelectric behavior. The energy storage density (728 mJ/cm3 at an electric field of 750 kV/cm) of the composite with 15 wt% of h-(BZT-BCT) is found to be much higher than those of the pure BZT-BCT sample, pure PVDF-HFP copolymer and their composites. Our work demonstrates the method of enhancing the functional properties through a suitable microstructure of composite materials with surface-hydroxylation of filler particles. • Ferroelectricity in virgin and hydroxylated (h-) BZT-BCT ceramic/PVDF-HFP copolymer composites is studied. • A 15 wt% concentration of h-(BZT-BCT) filler particles enhances packing density of composite by minimizing voids. • High packing density enhances interfacial interaction between h-(BZT-BCT) fillers and PVDF-HFP polymer. • Hydroxyl (–OH) ions on h-(BZT-BCT) particles facilitates formation of electroactive β-phase of PVDF-HFP. • Our work demonstrates a method to improve ferroelectricity and energy storage density of ceramic/polymer composites. [ABSTRACT FROM AUTHOR]