Nanocrystalline Sm0.5Sr0.5CoO3-δ synthesized using a chelating route for use in IT-SOFC cathodes: Microstructure, surface chemistry and electrical conductivity

Nanocrystalline Sm0.5Sr0.5CoO3_delta powders were synthesized by a chelating route using different polyfunctional H(x)APC acids (APC= aminopolycarboxylate; x=3, 4, 5). Different homologous aminopolycarboxylic acids, namely nitrilotriacetic (H(3)nta), ethylenediaminetetraacetic (H(4)edta), 1,2-cyclohexane-diaminetetracetic (H(4)cdta) and diethylenetriaminepentaacetic (H(5)dtpa) acid, were used as chelating agents to combine Sm, Sr, Co elements into a perovskite structure. The effects of the chelating agents on the crystalline structure, porosity, surface chemistry and electrical properties were investigated. The electrical properties of the perovskite-type materials emphasized that their conductivities in the temperature range of interest (600-800 degrees C) depend on the nature of the precursors as well as on the presence of a residual Co oxide phase as shown by XRD and XPS analysis. The surface chemistry and the surface stoichiometries were determined by XPS revealing a complex chemical behavior of Sr that exhibits a peculiar surface phase and bulk phase chemistry within the detected volume ( < 10 nm). (C) 2013 Elsevier Inc. All rights reserved.