Preparation and characterization of perovskite-type Ln′ x Ln″ 1–x CoO ₃ for electroceramic applications

Heteronuclear complexes of the type Ln′xLn″1 –x[Co(CN)6]·nH2O have been synthesized for potential applications in solid oxide fuel cells. SmxEr1 –xCo and SmxYb1 –xCo complexes crystallize in the orthorhombic system, as do LaxSm1 –xCo complexes for x= 0-0.6. A plot of the lattice parameters of the orthorhombic structures of the complexes as a function of reff[xrLn′+(l -x)rLn′] shows linear behaviour similar to that observed for the LnCo complexes. For the decomposed products, perovskite-type Ln′xLn″1 –xCoO3 oxides are obtained. The crystal structure of Ln′xLn″1 –xCoO3 is orthorhombic for 0.1080 < reff/nm < 0.1199 and hexagonal for reff > 0.1199 nm, while for reff < 0.1080 nm no perovskite-type oxide was formed. We suggest that the orthorhombic distortion parameter is greater than ca. 0.267 for reff < 0.1080 nm and therefore no perovskite-type oxide is formed.