BPN914: Elucidating Aging Mechanisms of Tin(IV) Oxide-based Gas Sensors


Despite decades of study and deployment, chemiresistive gas sensors based on SnO2 suffer from baseline drift due to aging of the SnO2 sensing material. In this work, we investigate how repeated, simulated operation of SnO2-based sensors causes irreversible changes in the electronic sensing behavior of SnO2, quantified through the bulk and inter-grain resistance of SnO2 as measured by potentiometric impedance spectroscopy (PIS). In tandem, we apply powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to link the observed changes in the bulk and inter-grain resistance to underlying structural and chemical changes. We propose that an observed increase in the bulk resistance caused by repeated annealing results from the repair of lattice defects in the SnO2 bulk, as supported by expansion of the lattice constant and relief of micro-strain observed via XRD. In contrast, we find that the inter-grain resistance decreases after repeated annealing, which suggests a change in population of O vacancies at or near the grain surfaces; we are currently investigating this hypothesis with near-surface chemical analysis from XPS, which indicates an increase in the relative abundance of Sn2+ to Sn4+, as well as an increase in an O 1s signal attributed to high-energy O sites that are suspected to be localized at surfaces and grain boundaries. Future work will center around extensions of XPS to confirm whether O vacancies are localized at surfaces and to examine how the population of O vacancies responds to different gas environments.

Project ended 09/08/2022

Publication date: 
August 22, 2022
Publication type: 
BSAC Project Materials (Final/Archive)
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