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

Abstract Nanocrystalline Sm 0.5 Sr 0.5 CoO 3− δ 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-cyclohexanediaminetetracetic (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 °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 (