TEMPERATURE-DEPENDENCE OF POSITRON-ANNIHILATION LIFETIME, FREE-VOLUME, CONDUCTIVITY, IONIC MOBILITY, AND NUMBER OF CHARGE-CARRIERS IN A POLYMER ELECTROLYTE POLYETHYLENE OXIDE COMPLEXED WITH NH4CLO4

Various physical properties of the solution-cast films of the proton c onducting polymer polyethylene oxide (PEG) complexed with ammonium per chlorate (NH4ClO4) have been studied in the temperature range 300-370 K. These properties studied by us include free volume by positron life time spectroscopy, ionic conductivity by impedance spectroscopy, ionic mobility by transient ionic current technique, number of charge carri ers, dielectric constant, etc. The hole volume and conductivity show a steep rise at T similar or equal to T-m (similar to 333 K). It appear s that the increase in free volume arises out of the increase in the s ize of the holes rather than an increase in their number. Although the free volume shows an increase around T-m, the measured ionic mobility does not show similar behavior. The increase in the conductivity at T -m is, therefore, ascribed to an increase in the number of charge carr iers at similar to T-m. A suitable dissociation model involving the di electric constant is proposed to explain this increase. The value of t he dissociation energy for PEO:NH4ClO4 has been determined to be 2.4 e V.