Arup Dey

Vibrational spectroscopy and ionic conductivity of polyethylene oxide-NaClO4-CuO nanocomposite.

Structure, morphology and thermal properties of polyethylene oxide (PEO) with sodium perchlorate (NaClO(4)) as electrolytic salt have been investigated by incorporating cupric monoxide (CuO) nanoparticles. Monoclinic CuO affects melting and glass transition temperatures of PEO-NaClO(4). Crystallinity and free ion concentration change with the variation of CuO concentration. The maximum ionic conductivity is observed for 10 wt.% CuO. Ionic conductivity follows Arrhenius type behavior as a function of temperature.

Size effect of cubic ZrO2 nanoparticles on ionic conductivity of polyethylene oxide-based composite

A solvent free solid composite polymer electrolyte (SCPE) film consisting of high molecular mass polyethylene oxide (PEO) with sodium perchlorate (NaClO4) as electrolytic salt and cubic zirconium oxide (ZrO2) nanoparticles as the filler has been prepared by solution casting technique to influence the transport properties. X-ray diffraction and Fourier transform infrared spectroscopy confirm the formation of the SCPE film, whereas atomic force microscopy reveals the presence of a network of interconnected nanoparticles forming uniform surface feature of relatively low roughness. The highest ionic conductivity (σ = 6.96 × 10-5 S-cm-1) for PEO25 - NaClO4 with 5 wt. % ZrO2 nanoparticles of the smallest size 4.5 nm is an order of magnitude higher than the pure PEO25 - NaClO4 at room temperature. The conductivity enhancement is due to the creation of additional sites and favorable conduction pathways for ionic transport through Lewis acid-base type interactions between the polar surface groups of the ceramic fi...

Large polaron tunneling and anomalous dielectric response in complex layered systems

Electrical conductivity and dielectric spectra of nanocomposites of conducting polyaniline and layered vanadyl phosphate VOPO4∙2H2O are studied at low temperature. Electrons and protons contribute to electrical conduction having the maximum conductivity of the order ∼10−5Scm−1. A discontinuity in electrical conductivity has been observed at about 210K. Conductivity with higher activation energy is dominated by protons. Smaller activation energy at lower temperature may be due to major electron conduction. Large polaron tunneling contributes to the electrical conduction process. The dielectric spectra exhibit anomalous frequency dispersion. Two frequency exponents in dielectric spectra are distinguished by considering intercluster and intracluster displacement of charge carriers.

Characterization and electrical properties of vanadyl phosphate-polypyrrole nanocomposites

Characterizations of layered vanadyl phosphate, VOPO4 · 2H2O, intercalated with conducting polypyrrole (PPY) have been carried out employing x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and high resolution transmission electron microscopy. Plate like structures are observed in scanning electron micrographs. The UV spectrum reveals the presence of PPY within nanocomposites in bimodal distribution. The room temperature conductivity of the nanocomposites is about 1000 times superior to the host vanadyl phosphate. Small polaron tunnelling is observed for smaller content of PPY. Electrical dc conductivity at low temperature is dominated by Motts one-dimensional variable range hopping for the higher concentration of PPY.

Mixed protonic-electronic conduction and dielectric response in layered vanadyl phosphate nanocomposites.

The layered vanadyl phosphate, VOPO(4)2H(2)O, is employed to prepare nanosized conducting polypyrrole by redox intercalation method. Transport and dielectric properties of various compositions have been investigated by impedance technique over a temperature range of 300-120 K. Grain boundary conductivity is larger than the bulk conductivity. The conductivity reveals a discontinuity at about 212-235 K. The conductivity is predominantly ionic at high temperature and electronic at low temperature. The dielectric spectra reveal a peak in the frequency range up to 2 MHz for higher concentration of intercalated polypyrrole. The activation energy of conductivity relaxation is different from that of total conductivity derived from the impedance plot.