Synthesis and gas-sensing characteristics of high thermostability gamma-Fe2O3 powder

gamma-FeOOH particles have been prepared by oxidizing Fe(CO3)(x)(OH)(2(1-x)), suspension which contains a proper amount of Y3+. Y2O3-doped gamma-Fe2O3, having tetragonal structure could be obtained by dehydrating the gamma-FeOOH powder. Thermostability of the gamma-Fe2O3 sample is studied by means of thermal gravimetric-differential thermal analysis and X-ray diffraction. It is found that the phase transition temperature of gamma-Fe2O3 --> alpha-Fe2O3 is up to 725 degrees C, which has the advantage of improving the long-term stability of gamma-Fe2O3-based sensors. The Y2O3-doped gamma-Fe2O3 sample calcined at 600 degrees C has much higher sensitivity and selectivity to hydrocarbon gases. When the sensors based on this material operate at 380 degrees C, the sensitivities are equal to 34 for 1000 ppm liquid petroleum gas (LPG), but only 3 for 1000 ppm H-2 or CO.