Proton conductivity of spin-coated Ta₂O₅·nH₂O amorphous thin films from peroxo-polytantalate solution

Peroxo-polytantalic acid (Ta-IPA) was obtained by a direct reaction of Ta(OC₂H₅) with H₂O₂. Using its water-based solution, amorphous thin films with excellent homogeneity could easily be fabricated on ITO-glass substrates by a conventional spin-coating technique. Electrical conductivity of this sample was measured with an ac impedance method, revealing that both temperature and humidity dependences of ionic conductivity (ca. 4.0×10^-1 S cm^-1 at 20°C) were quite small. Furthermore, all solid state ECD prototype was fabricated by combining this film electrolyte with electrochromic film (hydrous tungsten oxide film derived from peroxo-polytungstic acid). Electrochromic characteristics of this all solid state device were favorable.