The H diffusion parameters of fused silica and borosilicate glass at 673 to 1073K and 673 to 773K, respectively, were studied by a measuring apparatus developed based on the coulometric titration of an electrochemical cell made of an oxide protonic conductor. The measured values were in good agreement with those reported in the literature. From the H activity dependences of both permeability and diffusibility, it was concluded that in fused silica and borosilicate glass, most of the H permeation took place in the form of H molecules passing through the large holes induced in the structure with random arrangements of SiO4 tetrahedra. The solubility in the form of H molecules estimated by the permeability and diffusion coefficient values was two orders of magnitude smaller than that of H dissolved in the form of hydroxyl radicals. The migration rate of the H in the form of hydroxyl radicals was far smaller than the movement of H molecules. This fact was also suggested by the small H/D substitution rate observed by infrared absorption spectra.

Measurements of Hydrogen Permeation through Fused Silica and Borosilicate Glass by Electrochemical Pumping using Oxide Protonic Conductor. N.Kurita, N.Fukatsu, H.Otsuka, T.Ohashi: Solid State Ionics, 2002, 146[1-2], 101-11