Silica-gel films which contained HClO4, H3PW12O40, or (n-Bu)4NClO4, were prepared by using the sol-gel method and tetraethoxysilane plus the dopant. It was found that the HClO4- and H3PW12O40-doped films exhibited higher conductivities (0.01 to 0.1S/cm) at room temperature than did pure silica. In the case of (n-Bu)4NClO4-doped gel films, the conductivity was of the order of 10-5S/cm. A clear correlation was observed between the room-temperature conductivity and the wave-number of the OH band. This indicated that the stronger the O-H bonds in the silanol groups of silica gels, the easier was proton conduction. Conduction paths for protons formed in the doped silica gel structure, and the interaction between conduction paths and silanol groups affected the conductivities. The smaller interaction, which was indicated by higher values of the OH wave-number, was suggested to explain the higher proton conduction of doped silica gel films.

M.Tatsumisago, H.Honjo, Y.Sakai, T.Minami: Solid State Ionics, 1994, 74[3-4], 105-8