Preparation, characterization and gas-sensing properties of rare earth mixed oxides

Nanometer materials of rare earth mixed oxides REFeO3 (RE = Eu, Gd) with the structure of perovskite type were synthesized by sol-gel method in the citric acid system. The structure and crystal phase of the powders were characterized on an X-ray diffractometer. The shape and size were analyzed with the help of JEM-100X Transmission electron microscopy. The results show that the morphologies of the two perovskite-type oxides are spherical with the mean grain size of 20 and 21 nm, respectively. Their crystal structures show a certain amount of lattice distortion due to the decrease of grain size and the increase of surface area. Gas sensitivities of these two kinds of materials to C2H5OH, H2S, gasoline and H-2 were tested. The studies of gas-sensing characteristics show the sensitivities of EuFeO3 and GdFeO3 nanometer materials to gasoline are 39 and 45 at 340degreesC, respectively, and both of them have appropriate selectivity. So they are promising candidates for the detection of gasoline in monitoring environment. (C) 2003 Elsevier B.V. All rights reserved.