High Proton Conductivity in Porous P<INF>2</INF>O<INF>5</INF>−SiO<INF>2</INF> Glasses

High proton conducting P<INF>2</INF>O<INF>5</INF>−SiO<INF>2</INF> 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 SiO<INF>2</INF> and P<INF>2</INF>O<INF>5</INF>−SiO<INF>2</INF> 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 5P<INF>2</INF>O<INF>5</INF>−95SiO<INF>2</INF> glass heated at 700 °C and absorbing the water molecules.