CHARACTERISTICS OF ALPHA-FE2O3 THICK-FILM GAS SENSORS

Haematite (alpha-Fe2O3) with SO4(2-) and tin, as raw material, was prepared by a co-precipitation method. The alpha-Fe2O3-based thick film gas sensors were made by a screen printing technique. The microstructure of the raw material was affected by the hydrogen ion concentration which was controlled during the process of raw material preparation. Also, the pH value exhibited an effect on the sensitivity to gases for the thick film. It was thought that the sulphate ions localized in the thick film played an active role in hydrocarbon gas adsorption phenomena. Thick films of alpha-Fe2O3/alpha-Al2O3/Pd (78:20:2 by weight) had good adhesion to alumina substrates and exhibited relatively high sensitivity to CH4 at 350-degrees-C.