Characterization Of Humidity Sensor Research Articles

Effect of doping of alkali metal carbonate on humidity-sensing property of heat-treated SiO2 film.

SiO2 film consisting of a heat-treated mixture of silicone polymer and silica gel was prepared. Alkali metal carbonates (Li2CO3, Na2CO3 and K2CO3) were respectively doped into the film by a surface treatment. The humidity-sensing property was examined. The effects of heat treatment and exposure to high humidity air were studied after doping. By doping with different carbonates, the impedance of SiO2 films became low at various humidities. The impedance value of the doped films with dopant showed the order of Li2CO3>Na2CO3>K2CO3. After a final heat treatment and aging in high humidity air after doping, the humidity-sensing characteristics of the films scarecely change with exposure to indoor atmosphere. This effect of aging could be caused by the stable formation of hydration water to alkali metal carbonate.