Silica glasses with high surface area were prepared by the sol-gel method, the electrical conductivity of which was measured as a function of the content of adsorbed water. The glasses obtained by heating at 400-800°C had specific surface areas of 700-900 m 2 /g glass and exhibited room-temperature conductivities of 10 -6 -10 -3 S/cm by absorbing the water in pores. The activation energy for conduction linearly decreased with increasing logarithm of the product of proton and water concentration. On the other hand, the increase in conductivity was represented to be proportional to the logarithm of water concentration. Electrical conduction in glasses containing a large amount of water is related to the dissociation of protons from the SiOH bonds and the proton hopping through water molecules in pores. IntroductionProtons in glass are bound with oxygens to form hydroxyl groups attached to a network forming cations such as Si 4+ and P 5+ and are able to function as electrical charges when they are strongly hydrogen bonded in glasses. 1-3 Fast protonconducting glasses, if developed, have a high potential for use in clean energy fields, such as hydrogen gas sensors and hydrogen fuel cells. Recently, using a sol-gel technique, we succeeded in preparing P 2 O 5 -containing glasses with high conductivities of approximately 10 -4 -10 -2 S/cm at room temperature. 4-6 These high conductivities are considered to be achieved by fast proton mobility in the coexisting adsorbed molecular water in samples. The question how the adsorbed waters contribute to the high proton conductivity was not clear at that time.In the previous paper, we discussed the effect of molecular water on the proton conduction using sol-gel-derived porous silica glasses containing water molecules up to 2 wt %. 7 Since the water content is less than 2 wt %, all the water molecules are strongly hydrogen-bonded with SiOH on the pore surface. The activation energy for conduction linearly decreased with increasing logarithm of the product of proton and water concentration. We concluded that the proton conduction is associated with proton hopping between SiOH and water molecules and its activation energy is related to the energy necessary for the dissociation of the proton from SiOH and H 2 O. The dissociated proton from the hydroxyl groups moves between the SiOH and the H 2 O bound with SiOH. However, the effect of the molecular water adsorbed in excess of the number of SiOH groups still remains unknown. Molecular water acts sometimes in harmful ways to decrease the chemical durability of glasses. The search for the effect of water on proton conduction is necessary for both an understanding of the mechanism of proton conduction in glass and the development of fast proton conducting glasses.In this paper, we discuss how molecular water contributes to the proton conduction of water-containing glasses. Porous silica glasses with high specific surface areas were prepared by the sol-gel method, the conductivities of which were measured under a controlled water vapor...

High proton conducting P2O5−SiO2 glasses were prepared using the sol−gel method, the electrical conductivities of which were studied in relation to the pore structure and the adsorbed water. The pore properties of SiO2 and P2O5−SiO2 glasses were controlled by addition of formamide during the gel synthesis, the specific surface areas of which were changed from 200 to 900 m2/g-glass. These glasses absorb water molecules on exposure to a humid atmosphere. The conductivity increased with increasing logarithm of water concentration and reached a saturated value above the water vapor pressure of 0.8. The highest conductivity, 2 × 10-2 S/cm at room temperature, was achieved by 5P2O5−95SiO2 glass heated at 700 °C and absorbing the water molecules.

Detailed leakage current analysis of metal-insulator-metal capacitors with ZrO2, ZrO2/SiO2/ZrO2, and ZrO2/Al2O3/ZrO2 as dielectric and TiN electrodes J. Vac. Sci. Technol. B 31, 01A109 (2013); 10.1116/1.4768791Clusters dissolution of Yb3+ in codoped SiO2-Al2O3-P2O5 glass fiber and its relevance to photodarkening

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