Oxide composites have been produced by means of mechanical milling and sintering. Such materials consist of magnetic particles embedded in an insulating oxide matrix, which can have application as magnetic wave absorbers. Different systems have been investigated including MgO-MgFe2O4, FeO-Fe3O4 and other more complex ferrites. Milling induces the formation of a solid solution of cations and oxygen. Depending on temperature and system, sintering can produce a particle dispersion or simply the starting of the corresponding phase transformation. Spark plasma sintering was performed between 773 and 1373 K in order to reduce both processing time and temperature. High resolution (HREM) and conventional transmission electron microscopy show that an spinodal decomposition takes place in the system FeO-Fe3O4 during transformation from the solid solution.
Generally the oxygen lattice is unique throughout the material but there is a distinctive distribution of cations giving rise to a particle dispersioGn having an spinel structure in a insulating matrix with a NaCl cubic structure.