The simultaneous response of the work function and resistivity to H2 and H2S of some pure and doped SnO2 samples in the form of thick films is measured in humid laboratory air. The gas-sensitive layer of thick-film samples is screen printed on alumina substrates containing gold electrodes on a finger-like structure. Palladium and silver are used as catalytic activators in the SnO2. The work function change is measured with a vibrating capacitor (Kelvin probe) automatically compensated by a feedback system and with graphite as the reference electrode. Silver doping has a large effect on the response to H2S at temperatures around 150°C, but no effect is found in the case of exposure to H2 at these temperatures. Palladium doping has an effect only in the case of H2 exposure, the effect being strongest at lower temperatures around 150°C. The resistance changes give much higher values for the calculated work function changes as compared to the measured ones in the case of H2S exposure at 420 and 620 K, whereas in the case of H2 exposure, the measured one are higher and a linear dependence between the calculated and measured changes of work function is obtained.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Surfaces, Coatings and Films
- Metals and Alloys
- Electrical and Electronic Engineering
- Materials Chemistry