Sol-Gel Synthesis of Amorphous P₂O₅-TiO₂ Films and Their Electrical Properties

Abstract

Influence of humidity on the electrical conductivity on sol-gel derived amorphous titanium phosphate oxide films of nominal compositions of 1TiO2⋅9P2O5 to 9TiO2⋅1P2O5 (molar ratio) was investigated. The surface resistivity of a 3TiO2⋅7P2O5 film showed two order dependence on relative humidity change from 50RH% to 90RH% at 30°C. The surface conductivity of this film was 10-3S·cm-1 at 30°C, 90RH%. It is higher than that of alkaline-earth phosphate glasses (10-5S·cm-1 at around 100°C). Furthermore, the electrical resistance of this film decreased about one order after keeping it in a high humidity atmosphere of 90RH% at 30°C for 2.5h. This phenomenon implies that the proton conductivity was much enhanced by a large amount of molecular water (recognized at 3250cm-1 in FT-IR spectrum) which incorporated into the glass structure.