Synthesis and structural characterization of Co-doped lanthanum strontium titanates

Lanthanum strontium titanates based oxides, materials with perovskite-type crystal structure, are good candidates for symmetrical fuel cell electrodes. They can become good mixed conductors (electronic and ionic) and reach adequate electrocatalytic activity for both oxygen reduction and fuel oxidation reactions if the right doping or structural modification of the (La,Sr)TiO3 compound is performed. However, the crystallographic information reported in the literature indicates a noticeable lack of reproducibility, since it is strongly dependent on synthesis conditions. In this work, La0.4Sr0.6Ti1−yCoyO3+δ (0.0 ≤ y ≤ 0.5) synthesis by a low-temperature chemical route and its structural characterization by X-ray powder diffraction and transmission electron microscopy are reported. From Rietveld refinements results, charge compensation mechanisms are studied and their correlation with synthesis parameters is discussed. We show that the creation of Sr vacancies at the A-site of the perovskite-type structure is the main compensation mechanism and their concentration decreases with the incorporation of Co in the crystal structure.

▶ La0.4Sr0.6Ti1−yCoyO3 perovskites were proposed for symmetrical fuel cells. ▶ Samples were synthesized by a low temperature chemical route (850 °C). ▶ Rietveld method on synchrotron XRD data was used for structural characterization. ▶ Rhombohedral distortion was found on Co-doped samples and was maximum for y = 0.3. ▶ A-site vacancies is the dominant charge compensation mechanism for y ≤ 0.3 samples.