Coloring / bleaching processes of LixWO3 electrochrothismwere examined by means of emf, chronoamperometry, voltammetry and ac impedance measurements. Current-potential relation was found to be ohmic in the short time region and expressed by i=(Eapp-emf(x))/ R. Satisfactory fittings were obtained for chronoamperometry and voltammetry measurements on the basis of the assumption of diffusion-limited process with above i-E relation. It was elucidated from the detailed analysis of impedance that R was given by the summation of the resistances of solution, electrode, charge transfer and material transfer. It was newly found that diffusion coefficients for several WO3 films were in the range of 1.5 X 10-9 to 3 x 10-12 cm2,sec at 20°C and they were strongly dependent on water content in the electrolyte solution.
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