Physicochemical properties of non-stoichiometric oxides Mixed conductors: Part II

A. CANEIRO; L. MOGNI; N. GRUNBAUM; F. PRADO

JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY

SPRINGER

Lugar: Berlin; Año: 2011 vol. 104 p. 781 - 788

1388-6150

One of the most important challenges with solidoxide fuel cells (SOFC) is to find cathode materials withhigh enough catalytic activity for the dissociation of themolecular oxygen. Oxide mixed conductors with theperovskite structure (ABO3) and high Co content in the Bsite have been extensively studied to be used as cathode inSOFC. This is the second part of a review of high temperatureproperties of two mixed conductors systems. The firstpart was focused on the n = 2 Sr3FeMO6?d (M = Fe, Co,Ni) Rudlesdden Popper phases, while in this paper we discussthe thermodynamic and transport properties of theperovskite solid solution Sr1-xLaxFe0.2Co0.8O3-d (0 Bx B 0.4) in the temperature range 773 B T B 1173 K. Inparticular, the interest has been focused on the x = 0 sample,which exhibits large ionic conductivity values(ri *1 S cm-1), but suffers a structural transformationfrom cubic to orthorhombic symmetry because the orderingof the oxygen vacancies when the oxygen partial pressuredecreases. Measurements of the oxygen chemical potential(lO2 ) as function of oxygen content and temperature, coupledwith high temperature X-ray diffraction data, permittedus to broaden the knowledge of the T?d?p(O2) phase diagramfor the x = 0 sample. In addition, we have investigatedthe effects of the La incorporation on the stability range ofthe cubic phases of the Sr1-xLaxFe0.2Co0.8O3-d solidsolution.