Solvothermal synthesis of CoxFe3−xO4 spheres and their microwave absorption properties

The number of ferrous and ferric pairs in adjacent octahedral sites determines the real part of permittivity. The cobalt ratio in mixed spinels determines the crystallinity or number of defects, and ultimately the imaginary part of permittivity. At a high synthesis or calcination temperature, some cobaltous and ferrous atoms migrate from octahedral to tetrahedral sites.