Characterization of La2−xSrxCoTiO6 (0.6 ≤ x ≤ 1.0) series as new cathodes of solid oxide fuel cells

• A new double perovskite has been assessed as SOFC electrode.
• High electrical conductivity and stability in oxidizing atmospheres.
• Low thermal expansion.
• Low polarization resistance.

La2−xSrxCoTiO6 (0.6 ≤ x ≤ 1.0) compound series is prepared by Sr-substitution in the A-site of the perovskite by a modified Pechini procedure under air. Charge compensation as Sr2+ content increase occurs by Co2+ oxidation to Co3+. Reduced samples are obtained by further treatment under 5%H2/Ar and characterized by Neutron Powder Diffraction. Upon redution, Co3+ to Co2+ reduction and oxygen vacancies creation are detected. Dependence of total conductivity with temperature and pO2 exhibits a typical p-type semiconducting behaviour. Results show that the higher the Sr content, the higher holes (Co3+) concentration and consequently, La2−xSrxCoTiO6 (x = 1.0) shows the highest conductivity (13.23 S/cm at 1073 K in air). The negligible reactivity with YSZ, used as the electrolyte, of symmetrical cells under oxidant conditions and the moderate thermal expansion found by XRD point to their possible use as SOFC cathodes. Thus, La1.2Sr0.8CoTiO6-based cathodes display polarization resistance of 0.9 Ω cm2 at 1073 K in oxygen, only slightly above than the current state-of-the-art.