Synthesis, structure, and some physicochemical properties of SrCo1-xFexO3-δ

SrCo1-xFexO3-delta (x = 0.25, 0.50, 0.75, 1.00) solid solutions with the perovskite structure were prepared from nitrates by solid-state reactions in air at 1240 degrees C. The ratio of the lattice parameters a/c was found to increase with iron content: from 0.996 at x = 0.25 to 1.000 at x = 0.5 and 0.75 and to 1.003 at x = 1.00. The material with x = 0.75 has the largest unit-cell volume, which is probably associated with changes in the valence and spin states of iron and cobalt cations or ordering of these cations in the B site, resulting in a superstructure. In the temperature range 1240-1300 degrees C, the relative density of this material is higher than that of the other ceramics. Gas-tight, strong SrFeO3-delta ceramics could only be prepared by sintering in a temperature range as narrow as 1210 +/- 10 degrees C. At temperatures between 400 and 1000 degrees C, the equilibrium oxygen stoichiometry of the synthesized compounds varies reversibly both in air and oxygen and increases linearly with iron content.