Proton conductivity in silica gels

Commercial silica gel drying pearls were used in impedance measurements between ambient temperature and 300 °C in dry and humid atmospheres. A pronounced difference was seen supporting previous conclusions that proton conduction was operative in these amorphous samples. The same conclusion was reached on the basis of a fuel cell experiment at ambient temperature. A Nernst voltage close to the theoretical one was observed. Mechanical tests were carried out with silica gel plates made from the above material. Such plates displayed in the bending mode a time-dependent anelastic relaxation, i.e., a Gorsky effect, which arose from the long-range diffusion of protonic defects from the compressed to the dilated part of the plate. The chemical diffusivity and the density of the protonic defects could be determined. The same Gorsky effect may be expected in crystalline proton conductors, and also in Li-containing ceramics.