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

Barium stannate, a semiconducting oxide with cubic perovskite structure prepared by the thermal decomposition method, was incorporated with different noble metal additives. The gas sensing behavior of these materials to various 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 function of the noble metal additive. The results suggest that the greater the work function of the additive, the greater the depletion width of the semiconductor in air and the higher the sensitivity to the reducing gas. X-ray photoelectron spectroscopy studies have been carried out to understand the mechanism of sensing in these oxides. It has been established that in the case of Pd and Ag-incorporated BaSnO3 it is predominantly the electronic sensitization through a direct interaction between these metals and the semiconductor surface, while in case of Pt-incorporated BaSnO3 it is the chemical interaction which plays the major role in the gas sensing reaction. (C) 2001 Elsevier Science B.V. All rights reserved.