Abstract
Interdigital capacitors (IDCs) with gas-sensitive coatings are frequently used as gas sensors. In this work organically modified silicates (heteropolysiloxane, HPS) have been investigated as gas-sensitive coatings using impedance spectroscopy. The investigated dielectric gas sensors are thin-film IDCs on a silica glass substrate. When coated with an HPS film, the sensors have a high sensitivity to SO 2 (ranges 1-200 vpm and 10-6000 vpm) and a low cross-sensitivity to other gases. An electrical relaxation model for the sensitive film of these IDCs has been developed. The electrical relaxation of the bulk of the sensitive layer and the adsorbed gases is very similar to a Debye dipolar relaxation. A first attempt has been made to describe the electrode processes with Warburg impedance and a double-layer capacitance. The electrode processes and gravimetric adsorption isotherms indicate that SO 2 is absorbed into the bulk of the sensitive layer. Another result is that electrode processes could be one reason for the irreversible adsorption of SO 2.
Published Version
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