Improvement of response characteristics of TiO2 humidity sensors by simultaneous addition of Li2O and V2O5

Porous TiO₂ ceramics were prepared by adding various amounts of Li₂O and V₂O₅ and the humidity sensitivity of the resulting ceramics was investigated by means of electrical measurements, scanning electron microscopy and mercury intrusion porosimetry. Simultaneous addition of Li₂O and V₂O₅ to TiO₂ enabled sintering at temperatures as low as 700 °C and also decreased the impedance of the ceramics. Furthermore, in the ceramics including these additives simultaneously, excellent humidity sensitivity as well as good response characteristics were observed. The microstructures of these ceramics depended on the firing temperature and the amount and ratio of Li₂O/V₂O₅, and optimum humidity sensitivity was observed for the sample including both 0.25 mol% Li₂O and 0.75 mol% V₂O₅ fired at 700 °C. These results indicated that the humidity sensitivity and its response characteristics were closely related to the microstructure, and that improving the uniformity of microstructure is important for improving humidity sensitivity and its response characteristics.