Single-phase Y0.9Sr0.1CoO3-delta powders were prepared using a solution method based on the dissolution in aqueous media of stoichiometric amounts of yttrium, strontium and cobalt nitrates. Precursor powders were slowly heated from 90 to 950 T in air. Structural evolution was investigated by X-ray powder diffraction (XRD) as a function of increasing calcination temperature. Differential thermal analysis performed up to 1200 T was used to identify the temperature of formation for Y0.9Sr0.1CoO3-delta, which occurred at similar to912 degreesC. Single-phase polycrystalline powders having the perovskite structure were synthesized at 950 degreesC, their microstructure and particle size were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thick films of Y0.9Sr0.1CoO3-delta were deposited by the screen printing method on alumina substrates, in order to evaluate their electrical conductivity from room temperature to 700 degreesC. These measurements were performed in presence of air, oxygen and nitrogen. A semiconductor behavior with possible mixed ionic-electronic conductivity was observed. Sensitivity to nitrogen and oxygen showed a maximum at 579 and 557 degreesC, respectively. (C) 2004 Elsevier Ltd. All rights reserved.