Preliminary assessment of high temperature properties of cobalt free perovskites applied as SOFC cathode

J. F. BASBUS; F. PRADO; L. MOGNI; A. CANEIRO

Mar del Plata

Congreso; 4to Congreso Nacional y 3er Iberoamericano sobre Hidrógeno y Fuentes Sustentables de Energía; 2011

Instituto de Energía y Desarrollo Sustentable-CNEA

The cobalt-containing perovskite, such as Sm0.5Sr0.5CoO3−d LaxSr1−xCoyFe1−yO3−d and Ba0.5Sr0.5Co0.8Fe0.2O3−d have been extensively studied as cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC) because their low values of polarization resistance. However, the stability of these oxides for large periods of time could be compromised by the high thermal expansion coefficients (TECs) and the cobalt segregation. For these reasons and for the high cost of Co, it is interesting the search on novel cobalt-free perovskites cathodes. The Ba0.5Sr0.5Fe0.8M0.2O3-d (M = Ni, Cu, Zn) oxides with cubic perovskite structure were synthesized and their high temperature properties examined in order to evaluate these materials as a new cobalt-free cathodes for IT-SOFC. Particularly, the Ba0.5Sr0.5Fe0.8Ni.2O3-d composition is first time reported in this work. For comparison the Ba0.5Sr0.5Fe0.8Co0.2O3-d oxides is also characterized. The electrical conductivity and the thermal expansion coefficients are studied in air between room temperature and 900 °C. The four probe conductivities increase as a function of T until around 400- 600 °C and decreases for higher temperatures. The thermal expansion coefficient measured by dilatometry and the maximum conductivity values together with lattice parameters, oxygen content, and microstructure are analyzed as a function of the ionic radii of the M cations.