Noble metal additive modulation of gas sensitivity of BaSnO₃, explained by a work function based model

Abstract

Barium stannate, a semiconducting oxide with cubic perovskite structure, has been prepared by the thermal decomposition method. Of its several applications, this material has proved to be one of the successful candidates for chemical sensors to detect toxic and inflammable gases. BaSnO₃ was incorporated with different noble metal additives and the gas sensing behavior of these materials to various reducing gases like LPG, CO and CH₄ have been studied. A model for the electronic interaction between additives and semiconducting BaSnO₃ gas sensors is discussed. The model is based on the depletion layer that is created due to metal-semiconducting oxide contact. Change of the gas sensor characteristics before and after the exposure to the different test gases has been explained on the basis of work function of metal additives. The valence band X-ray photoelectron spectroscopy studies were used to support the results on the gas sensing characteristics in each of the noble metal incorporated BaSnO₃ sensor materials and bring out the difference in the sensing mechanisms in these materials.