Broad-Band Conductive Spectra of Polypropylene Oxide Complexed with LiClO_4

概要

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Broad-band conductive spectroscopy covering a 10 mHz-1 GHz frequency range has been employed to examine the ionic motions in polypropylene oxide (PPO) complexed with 0-1% LiClO_4 at temperatures from -60℃ to 100℃. The dc conduction appears as a plateau of the conductive spectra in their medium frequency range. As the frequency is lowered, the dc conduction is suppressed by the electrode polarization and results in a Cole-Cole conductive relaxation. At high frequencies, the conductive spectra are overtaken by the dielectric relaxations due to dipolar motions associated with the segmental- and normal-mode processes of PPO molecules. In addition, a new relaxation process was found, which is attributable to the ionic motion because the relaxation strength increases with LiClO_4 concentration in parallel with an increase of dc conductivity. This finding suggests that the dissociated ions undergo local fluctuational motion (ionic relaxation) prior to starting long-range diffusion (dc conduction). Analysis based on a dynamic bond percolation theory shows that this tonic relaxation occurs in harmony with segmental-mode motion while the dc conduction is associated with the normal-mode process through a renewal of local hopping probabilities.
社団法人応用物理学会の論文
1997-03-15