Improvements in α-Fe2O3 ceramic sensors for reducing gases by addition of Sb2O3

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The microstructure, electrical properties and gas-sensing characteristics of Sb-doped α-Fe2O3 were investigated. Powder precursors with Sb/Fe = 0–0.1 were prepared by chemical coprecipitation method. Sb-doped α-Fe2O3 powders were characterized by means of thermal gravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), BET surface area and scanning electron microscope (SEM). It was found that the raw powders underwent crystallization into the corundum structure of α-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 agglomerates. The doping of Sb2O3 decreased the sensor resistance by one order of magnitude and increased the sensitivities to some hydrocarbon gases markedly. The former can be attributed to the substitution of Sb5+ for Fe3+ sites in α-Fe2O3 generating more free electrons; the latter is closely related to Sb-doped samples accommodating a higher density of chemisorbed oxygen.

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