Sol-gel synthesis of proton-conducting amorphous films containing P2O5

Electrical properties of the sol-gel derived amorphous alms containing P2O5 have been investigated. In the binary system of P2O5-SiO2, the surface resistivities at 25 degrees C under a relative humidity ranging from 50 to 90%RH were 2-3 orders of magnitude higher than that of the P2O5-TiO2 films. In a nominal composition of P2O5 . 9SiO(2) (molar ratio), the conductivity at 25 degrees C of the him prepared by using H3PO4 for the starting materials of P was 10(-6) S.cm(-1). This was 1 or 2 orders of magnitude higher than that of the alms prepared by using partially hydrolyzed P2O5: PO[OCH(CH3)(2)](3-x)(OH)(x) or PO(OCH3)(3) as starting materials of P, respectively. In the former case of PO[OCH(CH3)(2)](3-x) (OH)(x), however, the conductivity of the him obtained from a coating solution kept for 40d after preparation increased up to 10(-6) S.cm(-1). In these alms, we observed absorption band at 1300 cm(-1), which was assigned to P=O stretching vibration. The high proton-conductivities come from the increase of hydrogen-bonded protons in the glass structure with increasing the P=O bonding content.