HUMIDITY SENSITIVITY OF NB2O5-DOPED TIO2 CERAMICS

The humidity sensitivity of Nb2O5-doped TiO2 has been investigated. The sensitivity is largely influenced by the microstructure, and better sensitivity can be observed in samples with higher porosity. Electrode materials also affect the sensitivity, and RuO2 is the most suitable material because the sample with the RuO2 electrode shows a lower impedance and better response. The response is largely dependent on the pore size. The impedance of the sample gradually increases with time, and IR measurements confirm that this increase is caused by the chemisorption of water molecules. Aging in a high-temperature, high-humidity atmosphere is effective for reducing or eliminating this increase in impedance, and a sample aged under appropriate conditions exhibits a completely stable humidity sensitivity. © 1990.