Synthesis of Plate-like Spinel Particles and Spinel-Hexaferrite Intergrowth Nanocomposite Particles Using the Hydrothermal Decomposition of Ba-Hexaferrite

A new strategy for the synthesis of particles of cubic magnetite spinel with an anisotropic plate-like shape and of spinel-hexaferrite intergrowth nanocomposite particles is presented. The strategy is based on the hydrothermal decomposition of presynthesized Ba-hexaferrite (BaFe 12 O 19 ) particles in the presence of NaHCO 3 and a hydrazine reducing agent. The Ba from the BaFe 12 O 19 preferentially reacts with CO 3 2− to form witherite (BaCO 3 ), resulting in the decomposition of the original hexaferrite particles into magnetite (Fe 3 O 4 ) platelets, or into spinel-hexaferrite intergrowth particles, when the reaction is incomplete. The intergrowth particles displayed hysteresis loops combining the soft magnetic properties of the spinel and the hard magnetic properties of the hexaferrite.