Stability of the infinite layer structure with iron square planar coordination

The synthesis of the complete solid solution of [Sr.sub.1-x][Ca.sub.x]Fe[O.sub.2] together with their thermal stability measured by in situ X-ray diffraction is described. The studies have shown that the infinite layer (IL) iron oxide is robust against substitution as well as temperature, which is attributed to the strong hybridization between Fe and O.