Improvements in alpha-Fe2O3 ceramic sensors for reducing gases by additionof Sb2O3

The microstructure, electrical properties and gas-sensing characteristics o f Sb-doped alpha-Fe2O3 were investigated. Powder precursors with Sb/Fe = 0- 0.1 were prepared by chemical coprecipitation method. Sb-doped alpha-Fe2O3 powders were characterized by means of thermal gravimetric-differential the rmal analysis (TG-DTA), X-ray diffraction (XRD), BET surface area and scann ing electron microscope (SEM). It was found that the raw powders underwent crystallization into the corundum structure of alpha-Fe2O3 at a temperature which increased somewhat with increasing Sb content; a proper amount of Sb doping suppressed both crystallite growth and the formation of hard agglom erates. The doping of Sb2O3 decreased the sensor resistance by one order of magnitude and increased the sensitivities to some hydrocarbon gases marked ly. The former can be attributed to the substitution of Sb5+ for Fe3+ sites in alpha-Fe2O3 generating more free electrons; the latter is closely relat ed to Sb-doped samples accommodating a higher density of chemisorbed oxygen . (C) 2000 Kluwer Academic Publishers.