Spinodal-type phase separation and proton conductivity of Al 2O3-doped porous glasses

Abstract

Porous glasses with the surface area of ≊300m2/g were prepared utilizing the spinodal-type phase separation of Al2O 3-doped Na2OB2O3SiO2 glasses. The proton conductivity under humidified conditions and their relations to the amount of doped Al2O3 were investigated. The proton conductivity of the glass doped with 2mol% of Al2O3 was about 6 times higher than that of the undoped glass. Fourier transform infrared (FTIR) measurements revealed that the absorption by the strongly hydrogen-bonded OH groups increased with increasing the amount of Al 2O3. Bond overlap populations (BOPs), which are directly related to the strength of the covalent bond, between the surface OH groups and an absorbed water molecule were calculated based on a firstprinciples theory (DVXα). The BOP values between O and H of the surface OH groups decreased by the Al2O3 doping. Substitution of Si atoms of the SiOSi silica networks with Al atoms, and formation of the AlOHSi bonds effectively improved the proton conductivity under humidified conditions. © 2010 The Ceramic Society of Japan.