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A general combined hydrothermal and annealing process for the fabrication of ferrite/perovskite oxide core/shell nanostructures was introduced. The coating of a perovskite oxide (ABO3) layer on spherical ferrite particles was performed in two steps. A dense and smooth amorphous layer containing B-site ions of the perovskite oxide was coated first via a controlled hydrolysis and aging process. During hydrothermal treatment and subsequent annealing process, the A-site ions were incorporated in situ into the as-coated amorphous layer preserving the spherical morphology. This synthesis of ferrite/perovskite oxide core/shell nanostructures was demonstrated in systems like Fe3O4/PbTiO3, γ-Fe2O3/PbTiO3, γ-Fe2O3/Pb(Zr,Ti)O3, CoFe2O4/BaTiO3, CoFe2O4/PbTiO3 and CoFe2O4/Pb(Zr,Ti)O3. This method allowed the shell thickness of the composite particles to be manipulated in a controlled manner with various core sizes. After the coating, the core and shell materials showed strong interactions and the ferroelectric layer dramatically affected the crystal structure, resistivity and magnetic properties of the composites.

Uniform magnetic Fe3O4 chains with an average length of 20 μm built up by tens of self-assembled microspheres have been synthesized via a simple surfactant-free hydrothermal method. A possible “nucleation-growth-connection-crystallization” growth mechanism has been proposed for the formation of the Fe3O4 chains.