Mechanism of highly sensitive and fast response Cr doped TiO2 oxygen gas sensor

The recent trend in the field of gas sensor research is to develop new sensing materials with higher sensitivity, selectivity and shorter response time. Titania (TiO2) doped with chromium has been investigated for its oxygen sensing properties. At an optimum Cr concentration of 0.4 wt.% the sensor shows a high sensitivity and shorter response time at 700 degrees C as compared to undoped material. This material also shows n to p-type transition above oxygen partial pressure of 1100 ppm. The x-ray photoelectron spectroscopy (XPS) results indicate changes in the oxidation states of Ti and Cr. The charge transfer mechanism at Ti and Cr sites has been discussed. A correlation between sensitivity and response time with shifts in binding energy (B.E.) of Ti 2p peak has been obtained. On the basis of these results, a sensitization mechanism in these sensors has been proposed. (C) 1997 Elsevier Science S.A. All rights reserved.