SYNTHESIS, STRUCTURE, AND SOME PHYSICOCHEMICAL PROPERTIES OF SrCo_1-xFeO_3-δ

摘要

SrCo_1-xFe_xO_3-δ(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 ℃.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℃,the relative density of this material is higher than that of the other ceramics. Gas-tight, strong SrFeO_3-δ ceramics could only be prepared by sintering in a temperature range as narrow as 1210±10℃.At temperatures between 400 and 1000℃,the equilibrium oxygen stoichiometry of the synthesized compounds varies reversibly both in air and oxygen and increases linearly with iron content.