Role of Water on Fast Proton Conduction in Sol-Gel Glasses

Fast proton-conducting P2O5-ZrO2-SiO2 glasses were prepared by sol-gel processing of metal alkoxides. Glasses heated to 150 to 400°C exhibited room temperature conductivities of 10–4 S/cm, larger by 2 order of magnitude than that of as-prepared gel, 3 × 10–7 S/cm at 30°C. The conductivity increased quadratically with the increasing product of proton and molecular water concentration. These high conductivities were regarded as fast proton transfer accelerated by molecular water bonded with the hydroxyl groups.