Sensing Properties of Nanostructured Sm 1-x Ba x CoO 3 (x = 0, 0.1) obtained by Solution Method

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Sensing Properties of Nanostructured Sm1-xBaxCoO3 (x = 0, 0.1) obtained by Solution Method Carlos R. Michel, Emilio Delgado and Israel Ceja Departamento de Física, CUCEI, Universidad de Guadalajara, Blvd. M. García Barragán 1421, Guadalajara, Jalisco 44430, México. ABSTRACT Some cobaltites with perovskite-type structure exhibit outstanding transport properties and high chemical activity, which make these materials suitable for applications in areas of gas sensors, heterogeneous catalysis, gas separation membranes and cathodes for solid oxide fuel cells. In this work, polycrystalline samples of Sm1-xBaxCoO3 (x = 0, 0.1) were prepared by an aqueous solution method using the corresponding nitrates. X-ray diffraction patterns of calcined samples showed that single-phase SmCoO3 was obtained at 900oC, whereas Sm0.9Ba0.1CoO3 was formed at 700oC. Electron microscopy images revealed that micron-sized particles were obtained for SmCoO3, whereas a nanostructured and nanoporous material was observed for Sm0.9Ba0.1CoO3. Electrical measurements made on thick films of the oxides revealed a semiconductor behavior in both phases, however Sm0.9Ba0.1CoO3 samples showed a larger conductivity compared with SmCoO3; dynamic response of resistance experiments made in air and CO2 revealed that Sm0.9Ba0.1CoO3 is selective to CO2. INTRODUCTION The development of nanostructured and nanoporous inorganic materials has been motivated by the challenges that involve their preparation and characterization, as well as their technological applications; in this field, however, only a limited number of oxide compositions have been studied in depth, such as TiO2, SnO2, SiO2, ZnO. The synthesis of other nanostructured oxides has received less attention. On the other hand, oxides with the perovskite-type structure (ABO3) have been of interest in several research areas such as anodes for solid oxide fuel cells, ceramic membranes for oxygen permeation, gas sensors, etc. [1-9] Specifically, in the case of cobaltites with the perovskite structure, most of the research has been focused on members of the solid solutions: M1-xSrxCoO3 (M = La or Nd). [10-11] In these oxides, the strontium-doping induces mixed-valence states: Co+2 and Co+3, which increases the oxygen non-stoichiometry, and at the same time improves the electrical conductivity. In order to investigate the formation of nanostructured and nanoporous perovskites: Sm1-xBaxCoO3, the synthesis of SmCoO3 and Sm0.9Ba0.1CoO3, was explored in this work. Structural characterization by X-ray powder diffraction showed that Sm0.9Ba0.1CoO3 has the perovskite structure, and the introduction of barium produced a nanostructured and nanoporous material, which was analyzed by SEM and TEM. Dynamic response of resistance measurements performed on thick-films of Sm0.9Ba0.1CoO3, suggest that this material can be use as a CO2 sensor.

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