Influence of tin oxide microstructure on the sensitivity to reductor gases

The response of tin oxide (SnO2) gas sensors is strongly dependent on the preparation parameters because these influence directly the internal porosity, degree of crystallinity and surface morphology. Sensor elements have been prepared by depositing nanocrystalline SnO2 at room temperature and at 250 degrees C on polycrystalline alumina substrates by reactive sputtering. It was observed that the response to gases was dependent on the deposition temperature due to the influence on the structure of the oxide. The best response to low concentrations of carbon monoxide and propanal was obtained from SnO2 sensors deposited at 250 degrees C. Microstructural studies of these devices were performed by transmission electron microscopy. The main variation observed in the SnO2 microstructure is the degree of porosity. The sensors prepared at 250 degrees C had a more compact columnar microstructure. (C) 1999 Elsevier Science S.A. All rights reserved.