X-ray photoelectron spectroscopic studies of noble metal-incorporated BaSnO3 based gas sensors

Barium stannate, a semiconducting oxide with cubic perovskite structure pre pared by the thermal decomposition method, was incorporated with different noble metal additives. The gas sensing behavior of these materials to vario us reducing gases like liquefied petroleum gas (LPG), CH4 and CO have been studied. The gas sensing characteristics established a relation between the sensitivity of the sensor to the different test gases and the work functio n of the noble metal additive. The results suggest that the greater the wor k function of the additive, the greater the depletion width of the semicond uctor in air and the higher the sensitivity to the reducing gas. X-ray phot oelectron spectroscopy studies have been carried out to understand the mech anism of sensing in these oxides. It has been established that in the case of Pd and Ag-incorporated BaSnO3 it is predominantly the electronic sensiti zation through a direct interaction between these metals and the semiconduc tor surface, while in case of Pt-incorporated BaSnO3 it is the chemical int eraction which plays the major role in the gas sensing reaction. (C) 2001 E lsevier Science B.V. All rights reserved.