Structure and electrical properties of tungsten oxide hydrate amorphous thin film

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An amorphous thin film can easily be fabricated by the spincoating technique using a solution of peroxo-polytungstic acid(WIPA), which is formed by the direct reaction of metallic tungsten with hydrogen peroxide. Amorphous W0_3・nH_20 given by heating such a film at 100-160ﾟC exhibits good and stable electrochromism similar to that of conventional evaporated WO_3 films. We examined the dynamics of coloration of those coated films on a newly developed analytical basis. The coloration dynamics was investigated by measuring the transition current when a sudden downward step of the potential was applied to a sample. The current didn't follow the Cottrell-type time dependency, which suggest the rate is noi controlled* by diffusion. The time dependency of current can. be explained by a Butler-Volmer type relationship, hence the dynamics was revealed to be controlled by the charge transfer step.Tantalum and Niobium based amorphous solids were prepared. by drying respective peroxo polyacids. Alternating current electrical conductivity measurement's were carried out with pellet samples. Each specimen showed similar temperature dependency indicating its proton conductive mechanism was the same. The conductivity of Ta-IPA solid was larger than those of the others. Conduction mechanisms are discussed in relation to the water content and the structure of these materials.Amorphous thin films Of MoO_3・nH_2O and (Mo, W) O_3・nH_2O are fabricated by the spin-coating technique from peroxopolymolybdate and peroxo-polytungstomolybdate solutions. Some fundamental electrochromic properties of these films were investigated in LiClO_4/propylenecarbonate solution. The colored films derived from MO-IPA exhibited stronger and flatter visible absorption spectra than tungsten-based film.